U.S. patent application number 16/855554 was filed with the patent office on 2020-08-06 for laser radiation system.
This patent application is currently assigned to Gigaphoton Inc.. The applicant listed for this patent is Gigaphoton Inc. KYUSHU UNIVERSITY, NATIONAL UNIVERSITY CORPORATION. Invention is credited to Hiroshi IKENOUE, Hiroaki OIZUMI, Osamu WAKABAYASHI.
Application Number | 20200251359 16/855554 |
Document ID | / |
Family ID | 1000004815767 |
Filed Date | 2020-08-06 |
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United States Patent
Application |
20200251359 |
Kind Code |
A1 |
WAKABAYASHI; Osamu ; et
al. |
August 6, 2020 |
LASER RADIATION SYSTEM
Abstract
A laser radiation optical system for laser doping and
post-annealing, the laser radiation system including A. a laser
apparatus configured to generate pulsed laser light that belongs to
an ultraviolet region, B. a stage configured to move a radiation
receiving object in an at least one scan direction, the radiation
receiving object being an impurity source film containing at least
an impurity element as a dopant and formed on a semiconductor
substrate, and C. an optical system including a beam homogenizer
configured to shape the beam shape of the pulsed laser light into a
rectangular shape and generate a beam for laser doping and a beam
for post-annealing that differ from each other in terms of a first
beam width in the scan direction but have the same second beam
width perpendicular to the scan direction.
Inventors: |
WAKABAYASHI; Osamu;
(Oyama-shi, JP) ; IKENOUE; Hiroshi; (Fukuoka-shi,
JP) ; OIZUMI; Hiroaki; (Oyama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gigaphoton Inc.
KYUSHU UNIVERSITY, NATIONAL UNIVERSITY CORPORATION |
Tochigi
Fukuoka |
|
JP
JP |
|
|
Assignee: |
Gigaphoton Inc.
Tochigi
JP
KYUSHU UNIVERSITY, NATIONAL UNIVERSITY CORPORATION
Fukuoka
JP
|
Family ID: |
1000004815767 |
Appl. No.: |
16/855554 |
Filed: |
April 22, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2017/045970 |
Dec 21, 2017 |
|
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16855554 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01S 3/005 20130101;
G02B 27/0961 20130101; H01S 3/10069 20130101; B23K 26/352 20151001;
H01S 3/034 20130101; C23C 14/48 20130101; H01L 21/67115 20130101;
C23C 14/54 20130101; H01S 3/11 20130101; H01S 3/225 20130101; B23K
26/0732 20130101; H01L 29/167 20130101; B23K 26/0876 20130101; H01L
21/0455 20130101; B23K 26/064 20151001; B23K 26/082 20151001; G02B
27/14 20130101; H01S 3/038 20130101; H01L 29/1608 20130101; G02B
27/0966 20130101; G02B 27/0933 20130101; C23C 14/18 20130101 |
International
Class: |
H01L 21/67 20060101
H01L021/67; G02B 27/09 20060101 G02B027/09; G02B 27/14 20060101
G02B027/14; H01S 3/11 20060101 H01S003/11; H01S 3/00 20060101
H01S003/00; B23K 26/064 20060101 B23K026/064; B23K 26/073 20060101
B23K026/073; B23K 26/082 20060101 B23K026/082; B23K 26/08 20060101
B23K026/08; B23K 26/352 20060101 B23K026/352; C23C 14/48 20060101
C23C014/48; C23C 14/54 20060101 C23C014/54; C23C 14/18 20060101
C23C014/18 |
Claims
1. A laser radiation system for laser doping and post-annealing,
the laser radiation system comprising: A. a laser apparatus
configured to generate pulsed laser light that belongs to an
ultraviolet region; B. a stage configured to move a radiation
receiving object in an at least one scan direction, the radiation
receiving object being an impurity source film containing at least
an impurity element as a dopant and formed on a semiconductor
substrate; and C. an optical system including a beam homogenizer
configured to shape a beam shape of the pulsed laser light into a
rectangular shape and generate a beam for laser doping and a beam
for post-annealing that differ from each other in terms of a first
beam width in the scan direction but have the same second beam
width perpendicular to the scan direction.
2. The laser radiation system according to claim 1, wherein the
beam homogenizer is configured to selectively generate the beam for
laser doping and the beam for post-annealing based on the pulsed
laser light incident from the laser apparatus.
3. The laser radiation system according to claim 2, further
comprising: D. a laser radiation controller configured to control
the beam homogenizer to switch the beam for laser doping to the
beam for post-annealing and vice versa.
4. The laser radiation system according to claim 3, wherein the
beam homogenizer includes a first fly-eye lens for laser doping, a
second fly-eye lens for post-annealing, and a first actuator
configured to move the first and second fly-eye lenses, and the
laser radiation controller is configured to control the first
actuator to selectively insert one of the first and second fly-eye
lenses into an optical path of the pulsed laser light.
5. The laser radiation system according to claim 3, wherein the
beam homogenizer includes a first cylindrical lens array, a second
cylindrical lens array, and a third cylindrical lens array disposed
in an optical path of the pulsed laser light and a second actuator
configured to change a gap between the first cylindrical lens array
and the second cylindrical lens array, and the laser radiation
controller is configured to cause the beam homogenizer to
selectively generate the beam for laser doping and the beam for
post-annealing by controlling the second actuator to control the
gap to change the first beam width.
6. The laser radiation system according to claim 3, wherein the
first beam width Bdx of the beam for laser doping satisfies
Expression (a) below, and the first beam width Bpx of the beam for
post-annealing satisfies Expression (b) below, Bdx=Et/(FdBy) (a)
Bpx=Et/(FpBy) (b) where Et represents pulse energy of the pulsed
laser light, Fd represents first fluence for laser doping, Fp
represents second fluence for post-annealing, and By represents the
second beam width.
7. The laser radiation system according to claim 6, wherein a first
scan speed Vdx, which is a moving speed of the radiation receiving
object in the scan direction in the laser doping satisfies
Expression (c) below, and a second scan speed Vpx, which is a
moving speed of the radiation receiving object in the scan
direction in the post-annealing satisfies Expression (d) below,
Vdx=fBdx/Nd (c) Vpx=fBpx/Np (d) where f represents a repetitive
frequency of laser oscillation performed by the laser apparatus, Nd
represents a first number of radiated pulses for laser doping, and
Np represents a second number of radiated pulses for
post-annealing.
8. The laser radiation system according to claim 1, wherein the
beam homogenizer is configured to generate the beam for
post-annealing along with the beam for laser doping based on the
pulsed laser light incident from the laser apparatus.
9. The laser radiation system according to claim 8, wherein the
stage is configured to move the radiation receiving object with the
radiation receiving object irradiated with the beam for laser
doping and the beam for post-annealing.
10. The laser radiation system according to claim 9, wherein the
stage is configured to move the radiation receiving object in such
a way that a region irradiated with the beam for laser doping is
shifted from a region irradiated with the beam for post-annealing
toward a front side of the scan direction.
11. The laser radiation system according to claim 10, wherein the
optical system includes a beam splitter configured to reflect part
of the pulsed laser light and transmit another part of the pulsed
laser light, the beam homogenizer includes a first beam homogenizer
disposed in an optical path of the light having passed through the
beam splitter and a second beam homogenizer disposed in an optical
path of the light having reflected off the beam splitter, and one
of the first and second beam homogenizers is configured to generate
the beam for laser doping, and another of the first and second beam
homogenizers is configured to generate the beam for
post-annealing.
12. The laser radiation system according to claim 11, wherein the
beam splitter is configured to be capable of changing reflectance
of light reflected off a region on which the pulsed laser light is
incident.
13. The laser radiation system according to claim 12, wherein the
first beam homogenizer is used to perform the laser doping, the
second beam homogenizer is used to perform the post-annealing, and
the reflectance R is so set as to satisfy Expressions (d) to (f)
below, .alpha.=Fp/Fd (d) .beta.=Np/Nd (e)
R=.alpha..beta./(1+.alpha..beta.) (f) where Fd represents first
fluence for laser doping, Fp represents second fluence for
post-annealing, Nd represents a first number of radiated pulses for
laser doping, and Np represents a second number of radiated pulses
for post-annealing.
14. The laser radiation system according to claim 13, wherein the
first beam width Bdx of the beam for laser doping satisfies
Expression (g) below, and the first beam width Bpx of the beam for
post-annealing satisfies Expression (h) below, Bdx=(1-R)Et/(FdBy)
(g) Bpx=REt/(FpBy) (h) where Et represents pulse energy of the
pulsed laser light and By represents the second beam width.
15. The laser radiation system according to claim 14, wherein a
scan speed Vx, which is a moving speed of the radiation receiving
object, satisfies Expression (i) below Vx=fBdx/Nd (i).
16. The laser radiation system according to claim 12, wherein the
second beam homogenizer is used to perform the laser doping, the
first beam homogenizer is used to perform the post-annealing, and
the reflectance R is so set as to satisfy Expressions (j) to (l)
below, .alpha.=Fd/Fp (j) .beta.=Nd/Np (k)
R=.alpha..beta./(1+.alpha..beta.) (l) where Fd represents first
fluence for laser doping, Fp represents second fluence for
post-annealing, Nd represents a first number of radiated pulses for
laser doping, and Np represents a second number of radiated pulses
for post-annealing.
17. The laser radiation system according to claim 16, wherein the
first beam width Bdx of the beam for laser doping satisfies
Expression (m) below, and the first beam width Bpx of the beam for
post-annealing satisfies Expression (n) below, Bdx=REt/(FdBy) (m)
Bpx=(1-R)Et/(FpBy) (n) where Et represents pulse energy of the
pulsed laser light and By represents the second beam width.
18. The laser radiation system according to claim 17, wherein a
scan speed Vx, which is a moving speed of the radiation receiving
object, satisfies Expression (o) below Vx=fBdx/Nd (o).
19. The laser radiation system according to claim 11, wherein the
first beam homogenizer includes a first cylindrical lens array, a
second cylindrical lens array, and a third cylindrical lens array
disposed in an optical path of the pulsed laser light and a third
actuator configured to change a gap between the first cylindrical
lens array and the second cylindrical lens array, and the second
beam homogenizer includes a fourth cylindrical lens array, a fifth
cylindrical lens array, and a sixth cylindrical lens array disposed
in the optical path of the pulsed laser light and a fourth actuator
configured to change a gap between the fourth cylindrical lens
array and the fifth cylindrical lens array.
20. The laser radiation system according to claim 1, wherein the
semiconductor substrate is an SiC semiconductor substrate, and the
impurity source film is an aluminum metal film.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation application of
International Application No. PCT/JP2017/045970, filed on Dec. 21,
2017, the entire contents of which are hereby incorporated by
reference.
BACKGROUND
1. Technical Field
[0002] The present disclosure relates to a laser radiation
system.
2. Related Art
[0003] A semiconductor is a material that forms an active element,
such as an integrated circuit, a power device, a light-emitting
diode (LED), a liquid crystal display, an organic
electro-luminescence (EL) display, and is a material essential to
manufacture an electronic device. To manufacture such an active
element, it is necessary to dope an impurity as a dopant into a
semiconductor substrate and then activate the impurity to achieve
n-type or p-type electric characteristics of the impurity.
[0004] In general, an impurity is doped into a semiconductor
substrate and activated in the semiconductor by using thermal
diffusion and ion injection. The thermal diffusion is a method for
thermally diffusing an impurity in a semiconductor substrate via
the surface thereof and further activating the impurity by heating
the substrate to a high temperature in a gas containing the
impurity.
[0005] The ion injection includes an ion injection step and a
thermal annealing step. The ion injection step is the step of
injecting the impurity into the semiconductor substrate by
irradiating the semiconductor substrate with an impurity ion beam
accelerated to a high speed. The thermal annealing step is the step
of repairing defects in the semiconductor substrate that result
from the impurity injection and activating the impurity by
imparting thermal energy to the semiconductor substrate. The ion
injection has excellent characteristics, for example, allows an ion
injection region to be locally set by using a mask, such as a
resist, and accurate control of the depth of the impurity
concentration. The ion injection is therefore widely used as a
technology for manufacturing an integrated circuit using silicon
(Si).
[0006] Silicon carbide (SiC) is being developed as a material of a
next-generation power device. SiC has a wide bandgap, dielectric
breakdown electric field characteristics about 10 times better than
those of Si, excellent thermal conductivity, and other properties
as compared with Si used as a semiconductor material in related
art. SiC is further characterized by thermochemical stability.
[0007] To form a transistor by using SiC, an impurity needs to be
doped into the SiC. Doping an impurity by using related-art ion
injection used to form an Si-based transistor, however. has a
problem of thermal damage of SiC, resulting in defects, which lower
the electric characteristics of the transistor.
[0008] To address the problem, laser doping has been studied as the
method for doping an impurity into SiC. The laser doping is a
method for forming an impurity source film containing a dopant on
the surface of a semiconductor substrate and irradiating the
impurity source film with laser light to introduce the impurity
contained in the impurity source film into the semiconductor
substrate.
CITATION LIST
Patent Literature
[0009] [PTL 1] JP-A-5-55259 [0010] [PTL 2] JP-A-8-139048 [0011]
[PTL 3] JP-A-8-264468 [0012] [PTL 4] US Patent Publication No.
2016/0247681
SUMMARY
[0013] A laser radiation system for laser doping and post-annealing
according to a viewpoint of the present disclosure includes:
[0014] A. a laser apparatus configured to generate pulsed laser
light that belongs to an ultraviolet region,
[0015] B. a stage configured to move a radiation receiving object
in an at least one scan direction, the radiation receiving object
being an impurity source film containing at least an impurity
element as a dopant and formed on a semiconductor substrate,
and
[0016] C. an optical system including a beam homogenizer configured
to shape a beam shape of the pulsed laser light into a rectangular
shape and generate a beam for laser doping and a beam for
post-annealing that differ from each other in terms of a first beam
width in the scan direction but have the same second beam width
perpendicular to the scan direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Embodiments of the present disclosure will be described
below only by way of example with reference to the accompanying
drawings.
[0018] FIG. 1 schematically shows the configuration of a laser
radiation system according to Comparative Example.
[0019] FIG. 2 is a perspective view showing the configuration of a
fly-eye lens.
[0020] FIG. 3A is a plan view of a radiation receiving object in
the form of a wafer, and
[0021] FIG. 3B shows the shape of an irradiated region.
[0022] FIG. 4 describes set values of first fluence Fd and second
fluence Fp.
[0023] FIG. 5 is a flowchart showing processes in laser doping
control and post-annealing control performed by a laser radiation
controller.
[0024] FIG. 6 shows a subroutine illustrating the details of the
process of reading first and second radiation conditions.
[0025] FIG. 7 shows a subroutine illustrating the details of the
process of causing a laser apparatus to perform adjustment
oscillation.
[0026] FIG. 8 shows a subroutine illustrating the details of the
process of calculating parameters for laser doping and
post-annealing.
[0027] FIG. 9 shows a subroutine illustrating the details of the
process of setting the parameters for laser doping.
[0028] FIG. 10 shows a subroutine illustrating the details of the
process of setting the parameters for post-annealing.
[0029] FIG. 11 shows a subroutine illustrating the details of the
process of performing the scan radiation in an axis-X
direction.
[0030] FIG. 12 schematically shows the configuration of a laser
radiation system according to a first embodiment.
[0031] FIG. 13A shows the configuration of a first fly-eye lens,
and FIG. 13B shows the configuration of a second fly-eye lens.
[0032] FIG. 14A shows an irradiated region of the radiation
receiving object irradiated with pulsed laser light in the laser
doping, and FIG. 14B shows the irradiated region of the radiation
receiving object irradiated with the pulsed laser light in the
post-annealing.
[0033] FIG. 15 is a first half of a flowchart showing processes in
the laser doping control and the post-annealing control performed
by laser radiation controller.
[0034] FIG. 16 is a second half of the flowchart showing the
processes in the laser doping control and the post-annealing
control performed by laser radiation controller.
[0035] FIG. 17 shows a subroutine illustrating the details of the
process of calculating the parameters for laser doping and
post-annealing.
[0036] FIG. 18 shows a subroutine illustrating the details of the
process of setting the parameters for laser doping.
[0037] FIG. 19 shows a subroutine illustrating the details of the
process of setting the parameters for post-annealing.
[0038] FIG. 20 shows a subroutine illustrating the details of the
process of switching a first beam width to another.
[0039] FIG. 21 schematically shows the configuration of a laser
radiation system according to a second embodiment.
[0040] FIG. 22A shows a beam homogenizer viewed along the axis-H
direction, and
[0041] FIG. 22B shows the beam homogenizer viewed along the axis-V
direction.
[0042] FIG. 23 shows a subroutine illustrating the details of the
process of calculating the parameters for laser doping and
post-annealing.
[0043] FIG. 24 shows a subroutine illustrating the details of the
process of setting the parameters for laser doping.
[0044] FIG. 25 shows a subroutine illustrating the details of the
process of setting the parameters for post-annealing.
[0045] FIG. 26 shows a subroutine illustrating the details of the
process of switching the first beam width to another.
[0046] FIG. 27 shows a scan path in a first variation.
[0047] FIG. 28 is a flowchart showing the processes in the laser
doping control and the post-annealing control performed by the
laser radiation controller.
[0048] FIG. 29 schematically shows the configuration of a laser
radiation system according to a second variation.
[0049] FIG. 30 schematically shows the configuration of a laser
radiation system according to a third embodiment.
[0050] FIG. 31 shows the configuration of a reflectance variable
beam splitter.
[0051] FIG. 32 shows the configuration of first and second beam
homogenizers.
[0052] FIG. 33A shows a scan path, and FIG. 33B shows the shape of
the irradiated region.
[0053] FIG. 34 is a flowchart showing the processes in the laser
doping control and the post-annealing control performed by the
laser radiation controller.
[0054] FIG. 35 shows a subroutine illustrating the details of the
process of calculating the parameters for laser doping and
post-annealing.
[0055] FIG. 36 shows a subroutine illustrating the details of the
process of setting the parameters for laser doping and
post-annealing.
[0056] FIG. 37 schematically shows the configuration of a laser
radiation system according to a fourth embodiment.
[0057] FIG. 38A shows the beam homogenizer viewed along the axis-H
direction, and
[0058] FIG. 38B shows the beam homogenizer viewed along the axis-V
direction.
[0059] FIG. 39 shows a variation of the laser apparatus.
[0060] FIG. 40 shows another variation of a laser radiation
apparatus.
[0061] FIG. 41 shows a variation of a radiation shield.
DETAILED DESCRIPTION
[0062] <Contents> [0063] 1. Overview [0064] 2. Comparative
Example [0065] 2.1 Configuration [0066] 2.2 Configuration of
fly-eye lens [0067] 2.3 Scan radiation control [0068] 2.4 Set value
of fluence of pulsed laser light [0069] 2.5 Set value of
transmittance of light passing through attenuator [0070] 2.6
Operation of laser radiation system [0071] 2.6.1 Main procedure
[0072] 2.6.2 Details of S110 [0073] 2.6.3 Details of S120 [0074]
2.6.4 Details of S150 [0075] 2.6.5 Details of S160 [0076] 2.6.6.
Details of S210 [0077] 2.6.7 Details of S170 [0078] 2.7 Problems
[0079] 3. First embodiment [0080] 3.1 Configuration [0081] 3.2
Operation of laser radiation system [0082] 3.2.1 Main procedure
[0083] 3.2.2 Details of S350 [0084] 3.2.3 Details of S360 [0085]
3.2.4 Details of S420 [0086] 3.2.5 Details of S370 [0087] 3.3
Effects [0088] 4. Second embodiment [0089] 4.1 Configuration [0090]
4.2 Method for setting second beam width [0091] 4.3 Operation of
laser radiation system [0092] 4.3.1 Main procedure [0093] 4.3.2
Details of S350' [0094] 4.3.3 Details of S360' [0095] 4.3.4 Details
of S420' [0096] 4.3.5 Details of S370' [0097] 4.4 Effects [0098] 5.
First variation [0099] 5.1 Scan radiation control [0100] 5.2
Operation of laser radiation system [0101] 5.3 Effects [0102] 6.
Second variation [0103] 7. Third embodiment [0104] 7.1
Configuration [0105] 7.2 Scan radiation control [0106] 7.3 Method
for setting reflectance [0107] 7.4 Operation of laser radiation
system [0108] 7.4.1 Main procedure [0109] 7.4.2 Details of S750
[0110] 7.4.3 Details of S760 [0111] 7.5 Effects [0112] 8. Fourth
embodiment [0113] 8.1 Configuration [0114] 8.2 Operation [0115] 8.3
Effects [0116] 9. Variation of laser apparatus [0117] 10. Other
variations
[0118] Embodiments of the present disclosure will be described
below in detail with reference to the drawings. The embodiments
described below show some examples of the present disclosure and
are not intended to limit the contents of the present disclosure.
Further, all configurations and operations described in the
embodiments are not necessarily essential as configurations and
operations in the present disclosure. The same component has the
same reference character, and no redundant description of the same
component will be made.
1. Overview
[0119] The present disclosure relates to a laser radiation system
configured to dope an impurity into a semiconductor substrate and
perform post-annealing for activation of the impurity by
irradiating a radiation receiving object that is an impurity source
film formed on the semiconductor substrate with pulsed laser
light.
2. Comparative Example
[0120] 2.1 Configuration of laser radiation system
[0121] FIG. 1 schematically shows the configuration of a laser
radiation system 2 according to Comparative Example. The laser
radiation system 2 includes a laser apparatus 3 and a laser
radiation apparatus 4. The laser apparatus 3 and the laser
radiation apparatus 4 are connected to each other via an optical
path tube 5.
[0122] The laser apparatus 3 includes a master oscillator MO, an
optical pulse stretcher (OPS) 10, a monitor module 11, a shutter
12, and a laser controller 13. The laser apparatus 3 is a
discharge-excitation-type laser apparatus configured to generate
pulsed laser light that belongs to the ultraviolet region by using
a laser gas containing F.sub.2, KrF, ArF, XeCl, or XeF as a laser
medium.
[0123] When the laser apparatus 3 is an F.sub.2 laser apparatus,
the center wavelength of the pulsed laser light is about 157 nm.
When the laser apparatus 3 is an ArF excimer laser apparatus, the
center wavelength of the pulsed laser light is about 193.4 nm. When
the laser apparatus 3 is a KrF excimer laser apparatus, the center
wavelength of the pulsed laser light is about 248.4 nm. When the
laser apparatus 3 is a XeCl excimer laser apparatus, the center
wavelength of the pulsed laser light is about 308 nm. When the
laser apparatus 3 is a XeF excimer laser apparatus, the center
wavelength of the pulsed laser light is about 351 nm.
[0124] The master oscillator MO includes a laser chamber 20, the
combination of a rear mirror 21a and an output coupler 21b, a
charger 23, and a pulse power module (PPM) 24. FIG. 1 shows the
internal configuration of the laser chamber 20 viewed along a
direction substantially perpendicular to the traveling direction of
the laser light.
[0125] The laser chamber 20 is a chamber configured to encapsulate
the laser gas, and a pair of electrodes 22a and 22b are disposed in
the laser chamber 20. The pair of electrodes 22a and 22b are
discharge electrodes configured to excite the laser medium by using
discharge that occurs between the electrodes.
[0126] The laser chamber 20 has an opening formed therein, and an
electric insulator 25 closes the opening. The electrode 22a is
supported by the electric insulator 25, and the electrode 22b is
supported by a return plate 20d. The return plate 20d is connected
to the inner surface of the laser chamber 20 via wiring that is not
shown. An electric conductor is buried in the electric insulator
25. The electric conductor is configured to apply high voltage
supplied from the PPM 24 to the electrode 22a.
[0127] The charger 23 is a DC power source configured to charge a
charging capacitor that is not shown but is provided in the PPM 24
with predetermined voltage. The PPM 24 includes a switch 24a
controlled by the laser controller 13. When the state of the switch
24a transitions from the OFF-state to the ON state, the PPM 24
produces pulsed high voltage from the electric energy held in the
charger 23 and applies the high voltage to the space between the
pair of electrodes 22a and 22b.
[0128] When the high voltage is applied to the space between the
pair of electrodes 22a and 22b, dielectric breakdown occurs in the
space between the pair of electrodes 22a and 22b, followed by
discharge. The energy of the discharge excites the laser medium in
the laser chamber 20, and the laser medium transitions to a high
energy level. The excited laser medium then transitions to a lower
energy level, and the laser medium emits light according to the
difference between the energy levels.
[0129] Windows 20a and 20b are provided at opposite ends of the
laser chamber 20. The light generated in the laser chamber 20 exits
out of the laser chamber 20 via the windows 20a and 20b.
[0130] The rear mirror 21a and the output coupler 21b form an
optical resonator. The rear mirror 21a is coated with a
high-reflectance film, and the output coupler 21b is coated with a
partial reflection film. The laser chamber 20 is disposed in the
optical path of the optical resonator. The rear mirror 21a is
therefore configured to reflect the light having exited out of the
laser chamber 20 via the window 20a at high reflectance and cause
the reflected light to return into the laser chamber 20 via the
window 20a. The output coupler 21b is configured to transmit part
of the light having exited out of the laser chamber 20 via the
window 20b and reflect the remainder of the light back into the
laser chamber 20.
[0131] The light having exited out of the laser chamber 20 thus
travels back and forth between the rear mirror 21a and the output
coupler 21b and is amplified whenever passing through the discharge
space between the electrodes 22a and 22b. Part of the amplified
light exits as the pulsed laser light via an output coupler 24.
[0132] The OPS 10 includes a beam splitter 10y and concave mirrors
10a to 10d. The OPS 10 is so disposed that the beam splitter 10y is
located in the optical path of the pulsed laser light outputted
from the master oscillator MO. The concave mirrors 10a to 10d form
a delay optical system.
[0133] The concave mirrors 10a to 10d are each a concave mirror
having substantially the same focal length F. For example, the
focal length F corresponds to the distance from the beam splitter
10y to the concave mirror 10a. The concave mirrors 10a to 10d are
configured to guide the light partially reflected off the beam
splitter 10y to the beam splitter 10y and erectly transfer the
light to the beam splitter 10y. The OPS 10 is configured to stretch
the pulses of the pulsed laser light inputted from the master
oscillator MO and output pulsed laser light having an extended
pulse period width.
[0134] The monitor module 11 is disposed in the optical path of the
pulsed laser light having exited out of the master oscillator MO.
For example, the monitor module 11 includes a beam splitter 11a and
an optical sensor 11b. The beam splitter 11a is configured to
transmit the pulsed laser light outputted from the OPS 10 at high
transmittance toward the shutter 12 and reflect part of the pulsed
laser light toward the optical sensor 11b. The optical sensor 11b
is configured to detect the pulse energy of the pulsed laser light
incident thereon and output data on the detected pulse energy to
the laser controller 13.
[0135] The laser controller 13 is configured to transmit and
receive a variety of signals to and from a laser radiation
controller 31, which is provided in the laser radiation apparatus
4. The laser controller 13 is configured to receive a light
emission trigger Tr, target pulse energy Et, and other data from
the laser radiation controller 31. The laser controller 13 is
configured to transmit a charging voltage setting signal to the
charger 23 and transmit a signal configured to turn on or off the
switch 24a to the PPM 24.
[0136] The laser controller 13 is configured to receive the pulse
energy data from the monitor module 11 and refer to the received
pulse energy data to control the charging voltage provided by the
charger 23. Controlling the charging voltage provided by the
charger 23 allows control of the pulse energy of the pulsed laser
light.
[0137] The shutter 12 is disposed in the optical path of the pulsed
laser light having passed through the beam splitter 11a of the
monitor module 11. The laser controller 13 is configured to close
the shutter 12 after the laser oscillation starts but before the
difference between the pulse energy received from the monitor
module 11 and the target pulse energy Et falls within an acceptable
range. When the difference between the pulse energy received from
the monitor module 11 and the target pulse energy Et falls within
the acceptable range, the laser controller 13 opens the shutter 12.
The laser controller 13 is configured to transmit a preparation
completion signal Rd, which represents that the light emission
trigger Tr, which triggers the pulsed laser light, is receivable,
to the laser radiation controller 31 in synchronization with a
signal configured to open the shutter 12.
[0138] The laser radiation apparatus 4 includes an enclosure 30,
the laser radiation controller 31, a table 32, an XYZ stage 33, a
frame 34, a radiation shield 35, and an optical system 40. The
optical system 40 is disposed in the enclosure 30. The enclosure
30, the XYZ stage 33, and the radiation shield 35 are fixed to the
frame 34.
[0139] A radiation receiving object 50, which is irradiated with
the pulsed laser light from the laser radiation apparatus 4, is
placed on the table 32. The radiation receiving object 50 is made
of a semiconductor material used to form a power device, such as
SiC, diamond, and GaN. SiC does not necessarily have a specific
crystal structure and is, for example, 4H--SiC. The radiation
receiving object 50 includes a semiconductor substrate 51, which is
made of any of the semiconductor materials described above, and an
impurity source film 52, which is formed on the surface of the
semiconductor substrate 51. The impurity source film 52 is a film
containing at least an impurity element as a dopant.
[0140] To convert the semiconductor substrate 51 into a p-type
semiconductor substrate in the doping process, an aluminum metal
film containing the aluminum element as the p-type dopant is, for
example, used as the impurity source film 52. To convert the
semiconductor substrate 51 into an n-type semiconductor substrate
in the doping process, for example, a nitride film containing the
nitrogen element as the n-type dopant, such as an SiN film, is used
as the impurity source film 52.
[0141] The XYZ stage 33 is configured to movably support the table
32. The XYZ stage 33 is configured to move the table 32 in axis-X,
axis-Y, and axis-Z directions in accordance with a control signal
inputted from the laser radiation controller 31. The XYZ stage 33
is configured to change the position of the table 32 in the axis-X
or axis-Y direction to move a region of the surface of the
radiation receiving object 50 that is the region irradiated with
the pulsed laser light. The axis-Z direction is parallel to the
optical axis of the pulsed laser light outputted from the optical
system 40. The axis-X and axis-Y directions are perpendicular to
each other and are each perpendicular to the axis-Z direction.
[0142] The optical system 40 includes high-reflectance mirrors 41a
to 41c, an attenuator 42, a beam homogenizer 43, and a transfer
optical system 44. The high-reflectance mirrors 41a to 41c are
configured to reflect the pulsed laser light, which belongs to the
ultraviolet region, at high reflectance. The high-reflectance
mirror 41a is so disposed that the high-reflectance mirror 41a
reflects the pulsed laser light incident from the laser apparatus 3
via the optical path tube 5 and the reflected pulsed laser light
passes through the attenuator 42 and is incident on the
high-reflectance mirror 41b. The high-reflectance mirrors 41a to
41c are each formed, for example, of a transparent substrate made
of synthetic quartz or calcium fluoride (CaF.sub.2) crystal and
having a surface coated with a reflection film configured to
reflect the pulsed laser light at high reflectance.
[0143] The attenuator 42 is disposed in the optical path between
the high-reflectance mirrors 41a and 41b. The attenuator 42
includes two partial reflection mirrors 42a and 42b and rotary
stages 42c and 42d. The rotary stage 42c is configured to hold and
rotate the partial reflection mirror 42a to change the angle of
incidence of the pulsed laser light incident on the partial
reflection mirror 42a. The rotary stage 42d is configured to hold
and rotate the partial reflection mirror 42b to change the angle of
incidence of the pulsed laser light incident on the partial
reflection mirror 42b.
[0144] The partial reflection mirrors 42a and 42b are each an
optical element having transmittance that changes in accordance
with the angle of incidence of the pulsed laser light. The rotary
stages 42c and 42d are configured to adjust the inclination angle
of the partial reflection mirrors 42a and 42b in such a way that
the angles of incidence of the pulsed laser light incident on the
partial reflection mirrors 42a and 42b coincide with each other and
the partial reflection mirrors 42a and 42b have desired
transmittance.
[0145] The rotary stages 42c and 42d are driven by control signals
inputted from the laser radiation controller 31 to control the
transmittance of the attenuator 42. The pulsed laser light having
entered the attenuator 42 is attenuated in accordance with the
transmittance controlled by the control signals and exits out of
the attenuator 42.
[0146] The high-reflectance mirror 41b is so disposed that the
pulsed laser light incident from the attenuator 42 is reflected off
the high-reflectance mirror 41b and the reflected pulsed laser
light passes through the beam homogenizer 43 and is incident on the
high-reflectance mirror 41c.
[0147] The beam homogenizer 43 is disposed in the optical path
between the high-reflectance mirrors 41b and 41c. The beam
homogenizer 43 includes a fly-eye lens 45 and a condenser lens 46.
The fly-eye lens 45 is disposed on the upstream of the condenser
lens 46. The pulsed laser light incident from the high-reflectance
mirror 41b passes through the fly-eye lens 45 and the condenser
lens 46, which are configured to convert the pulsed laser light
into Koehler illumination light in the focal plane of the condenser
lens 46, and the Koehler illumination light has an optical
intensity distribution homogenized in a predetermined beam shape.
The fly-eye lens 45 shapes the beam shape of the pulsed laser light
in a cross section perpendicular to the optical axis thereof into a
rectangular shape. The pulsed laser light having exited out of the
fly-eye lens 45 passes through the condenser lens 46, the focal
plane of which is illuminated with the pulsed laser light in the
form of Koehler illumination, and the pulsed laser light is
incident on the high-reflectance mirror 41c.
[0148] The transfer optical system 44 is disposed in the optical
path of the pulsed laser light reflected off the high-reflectance
mirror 41c. The transfer optical system 44 is formed of the
combination of a plurality of lenses. The transfer optical system
44 may be a reduction projection optical system. The transfer
optical system 44 is configured to transfer the rectangular beam
formed by the beam homogenizer 43 onto the surface of the radiation
receiving object 50 via a window 36.
[0149] The window 36 is disposed in the optical path between the
transfer optical system 44 and the radiation receiving object 50
and fixed to an opening formed in the enclosure 30 with the gap
between the window 36 and the opening sealed with an O ring that is
not shown. The window 36 is a transparent substrate made of
synthetic quartz or CaF.sub.2 crystal, and the opposite surfaces of
the window 36 may each be coated with a reflection suppression
film.
[0150] The enclosure 30 is provided with an intake port 30a, via
which a first purge gas is sucked into the enclosure 30, and a
discharge port 30b, via which the first purge gas is discharged out
of the enclosure 30. For example, the first purge gas is nitrogen
(N.sub.2) gas. An intake tube and a discharge tube that are not
shown are connected to the intake port 30a and the discharge port
30b, respectively. The gaps between the intake port 30a and the
intake tube connected thereto and between the discharge port 30b
and the discharge tube connected thereto are each so sealed with an
O ring that is not shown that contamination in the enclosure 30 due
to outside air is suppressed. A first purge gas supply source 37,
which supplies the first purge gas, is connected to the intake port
30a. The first purge gas purges the interior of the enclosure
30.
[0151] The portion where the optical path tube 5 is connected to
the laser radiation apparatus 4 and portion where the optical path
tube 5 is connected to the laser apparatus 3 are each so configured
that the gap between the optical path tube 5 and the apparatus is
sealed with an O ring that is not shown. The first purge gas purges
the interior of the optical path tube 5.
[0152] The radiation shield 35 is configured to surround the
radiation receiving object 50 supported by the table 32. The
radiation shield 35 is so sized as to surround the entire table 32
and XYZ stage 33 and is fixed to the frame 34. An opening connected
to the window 36 provided in the enclosure 30 is formed in the
upper surface of the radiation shield 35. The gap between the
opening and the window 36 is sealed with an O ring that is not
shown.
[0153] The radiation shield 35 is configured to be capable of
filling the portion between the window 36 and the radiation
receiving object 50 with a second purge gas. The radiation shield
35 is provided with an intake port 35a, via which the second purge
gas is sucked into the radiation shield 35, and a discharge port
35b, via which the second purge gas is discharged out of the
radiation shield 35. The second purge gas is an inert gas hardly
containing oxygen and is, for example, argon gas (Ar) or helium gas
(He). The second purge gas may be an inert gas having oxygen
concentration that does not produce any oxide on the semiconductor
surface when the semiconductor material is irradiated with the
laser light. A second purge gas supply source 38, which supplies
the second purge gas, is connected to the intake port 35a. The
second purge gas purges the interior of the radiation shield
35.
[0154] The laser radiation controller 31 is configured to output
the light emission trigger Tr at a predetermined repetitive
frequency f to the laser controller 13. The master oscillator MO is
configured to accordingly perform the laser oscillation at the
repetitive frequency f. The laser radiation controller 31 includes
a storage that is not shown but is configured to store a first
radiation condition under which a beam for laser doping is radiated
and a second radiation condition under which a beam for post
annealing is radiated.
[0155] The first radiation condition contains fluence Fd and the
number of radiated pulses Nd of the beam for laser doping, which is
the pulsed laser light with which the radiation receiving object 50
is irradiated in the laser doping. The second radiation condition
contains fluence Fp and the number of radiated pulses Np of the
beam for post-annealing, which is the pulsed laser light with which
the radiation receiving object 50 is irradiated in the
post-annealing. The fluence Fd is hereinafter referred to as first
fluence Fd. The number of radiated pulses Nd is referred to as a
first number of radiated pulses Nd. The fluence Fp is hereinafter
referred to as second fluence Fp. The number of radiated pulses Np
is referred to as a second number of radiated pulses Np. The first
and second radiation conditions stored in the storage can be
overwritten as appropriate by an external apparatus that is not
shown.
[0156] The laser radiation controller 31 is configured to control
the XYZ stage 33 in the laser doping and the post-annealing to
perform scanning radiation in which the radiation receiving object
50 is radiated with the pulsed laser light while moving the
radiation receiving object 50 in the plane XY. The laser radiation
controller 31 is configured to calculate first transmittance Td of
light passing through the attenuator 42 and a first scan speed Vdx,
which are set in the laser doping, based on the first radiation
condition. The laser radiation controller 31 is further configured
to calculate second transmittance Tp of light passing through the
attenuator 42 and a second scan speed Vpx, which are set in the
post-annealing, based on the second radiation condition. Details of
the above will be described below.
[0157] 2.2 Configuration of Fly-Eye Lens
[0158] The configuration of the fly-eye lens 45 provided in the
beam homogenizer 43 will next be described. FIG. 2 shows the
configuration of the fly-eye lens 45. In FIG. 2, an axis-I
direction represents the traveling direction of the pulsed laser
light. Axis-V and axis-H directions are perpendicular to each other
and further perpendicular to the traveling direction of the pulsed
laser light.
[0159] The fly-eye lens 45 is formed by processing a transparent
substrate made of synthetic quartz or calcium fluoride (CaF.sub.2)
crystal. A plurality of first concave cylindrical surface 451 each
having a first radius of curvature in the axis-V direction and
extending in the axis-H direction are arranged in the axis-V
direction at first intervals Lv on a first surface of the fly-eye
lens 45 that is the surface on which the pulsed laser light is
incident. A plurality of second concave cylindrical surface 452
each having a second radius of curvature in the axis-H direction
and extending in the axis-V direction are arranged in the axis-H
direction at second intervals Lh on a second surface of the fly-eye
lens 45 that is the surface opposite the first surface. The first
interval Lv is smaller than the second interval Lh.
[0160] The first radius of curvature of the first cylindrical
surfaces 451 and the second radius of curvature of the second
cylindrical surfaces 452 are so set that the focal position of the
concave lens formed by the first cylindrical surface 451
substantially coincides with the focal position of the concave lens
formed by the second cylindrical surface 452.
[0161] When the pulsed laser light is incident on the fly-eye lens
45, a secondary light source as a planar light source is produced
in the focal positions of the first cylindrical surfaces 451 and
the second cylindrical surfaces 452. The condenser lens 46 is
configured to cause the pulsed laser light having exited out of the
fly-eye lens 45 to form Koehler illumination in the position of the
focal plane of the condenser lens 46. The beam shape at the region
illuminated with the Koehler illumination is the shape of one lens
that forms the fly-eye lens 45, that is, a shape similar to the
oblong having the length of Lv in the axis-V direction and the
length of Lh in the axis-H direction. That is, the beam shape of
the pulsed laser light in a cross section perpendicular to the
optical axis is shaped by the beam homogenizer 43 into a
rectangular shape.
[0162] 2.3 Scan Radiation Control
[0163] Scan radiation control performed by the laser radiation
controller 31 will next be described. FIG. 3A shows the radiation
receiving object 50, which is the semiconductor substrate 51
described before in the form of a wafer. A plurality of chip
formation regions 53 are two-dimensionally arranged on the
semiconductor substrate 51 in the axis-X and axis-Y directions. The
chip formation regions 53 each have a rectangular shape.
[0164] In FIG. 3A, reference character A represents the beam shape
of the pulsed laser light which exits out of the beam homogenizer
43 and travels through the high-reflectance mirror 41c and the
transfer optical system 44 and with which the radiation receiving
object 50 is irradiated, that is the irradiated region. The
irradiated region A has a rectangular shape and has a first beam
width Bx in the axis-X direction and a second beam width By in the
axis-Y direction, as shown in FIG. 3B. The second beam width By is
greater than the first beam width Bx. That is, the pulsed laser
light has a substantially linear beam shape. It is preferable that
the second beam width By is greater than the first beam width Bx
multiplied by 5 but smaller than the first beam width Bx multiplied
by 1000.
[0165] The second beam width By is substantially equal to a width
Cy of each of the chip formation regions 53 in the axis-Y
direction. The width Cy represents the axis-Y-direction minimum
width of each of the chip formation regions 53 of the semiconductor
substrate 51 that are divided into chips, that is, the dicing
interval in the axis-Y direction. The second beam width By is not
limited to the width Cy and may be a value that satisfies the
following Expression (1).
By=nCy (1)
where n is an integer greater than or equal to 1.
[0166] The laser radiation controller 31 is configured to perform
the scan radiation by controlling the XYZ stage 33 to linearly move
the radiation receiving object 50 at a fixed speed in the axis-X
direction relative to the irradiated region A irradiated with the
pulsed laser light. The moving speed of the radiation receiving
object 50 in the laser doping is the first scan speed Vdx described
before, and the moving speed of the radiation receiving object 50
in the post-annealing is the second scan speed Vpx described
before. Reference character Sd represents a first scan path in the
laser doping. Reference character Sp represents a second scan path
in the post-annealing. In the present Comparative Example, the
first scan path Sd coincides with the second scan path Sp.
[0167] The laser radiation controller 31 is configured to calculate
the first scan speed Vdx in such a way that the number of pluses of
the pulsed laser light with which the position of each of the chip
formation regions 53 is irradiated is equal to the first number of
radiated pulses Nd described before. Specifically, the laser
radiation controller 31 is configured to use data on the first
number of radiated pulses Nd, the repetitive frequency f, and the
first beam width Bx to calculate the first scan speed Vdx based on
Expression (2) below.
Vdx=fBx/Nd (2)
[0168] The laser radiation controller 31 is configured to calculate
the second scan speed Vpx in such a way that the number of pluses
of the pulsed laser light with which the position of each of the
chip formation regions 53 is irradiated is equal to the second
number of radiated pulses Np described before. Specifically, the
laser radiation controller 31 is configured to use data on the
second number of radiated pulses Np, the repetitive frequency f,
and the first beam width Bx to calculate the second scan speed Vpx
based on Expression (3) below.
Vpx=fBx/Np (3)
[0169] To start the laser doping, the laser radiation controller 31
is configured to set the irradiated region A in an initial position
IP in the vicinity of a first chip formation region 53a located in
an end portion of a first row and start the scan radiation toward
the positive side of the axis-X direction at the first scan speed
Vdx along the first scan path Sd. When the irradiated region A
passes through a second chip formation region 53b located at the
last end of the first row, the laser radiation controller 31 moves
the irradiated region A toward the positive side of the axis-Y
direction. The laser radiation controller 31 is thereafter
configured to perform the scan radiation toward the negative side
of the axis-X direction from a third chip formation region 53c
located in an end portion of a second row. When the irradiated
region A passes through a fourth chip formation region 53d located
at the last end of the second row, the laser radiation controller
31 moves the irradiated region A toward the positive side of the
axis-Y direction by one row.
[0170] The laser radiation controller 31 is configured to
repeatedly perform the scan radiation described above and causes
the irradiated region A to return to the initial position IP when
the irradiated region A passes through a fifth chip formation
region 53e located at the last end of the last row. The laser
radiation controller 31 is thereafter configured to perform the
scan radiation for post-annealing at the second scan speed Vpx
along the second scan path Sp.
[0171] 2.4 Set Value of Fluence of Pulsed Laser Light
[0172] The fluence of the pulsed laser light in the laser doping
and the post-annealing will next be described. The fluence used
herein is the energy density (J/cm.sup.2) per pulse of the pulsed
laser light on the surface of the radiation receiving object 50.
The laser radiation controller 31 is configured to set the first
fluence Fd in the laser doping and the second fluence Fp in the
post-annealing by controlling the transmittance of light passing
through the attenuator 42.
[0173] FIG. 4 describes set values of the first fluence Fd and the
second fluence Fp. The first fluence Fd is so set as to fall within
the range that satisfies Expression (4) below.
Fath Fd<Fdth (4)
[0174] Reference character Fath is a fluence threshold that causes
ablation in the impurity source film 52 formed on the surface of
the semiconductor substrate 51 when the radiation receiving object
50 is irradiated with the pulsed laser light having the first
number of radiated pulses Nd. Reference character Fdth is a fluence
threshold that causes damage at the surface of the semiconductor
substrate 51 when the radiation receiving object 50 is irradiated
with the pulsed laser light having the first number of radiated
pulses Nd. When the first fluence Fd is so set as to fall within
the range expressed by Expression (4) described above, the impurity
source film 52 can be ablated, and the impurity can be doped into
the semiconductor substrate 51 with no damage at the surface of the
semiconductor substrate 51.
[0175] The second fluence Fp is in principle preferably so set as
to fall within the range that satisfy (5) below and more preferably
so set as to fall within the range that satisfy (6) below.
Fpth.ltoreq.Fp<Fdth (5)
Fpth.ltoreq.Fp<Fd (6)
[0176] Reference character Fpth is a fluence threshold that allows
repair of defects in the semiconductor substrate 51 that result
from the doping when the semiconductor substrate 51 having
undergone the doping is irradiated with the pulsed laser light
having the second number of radiated pulses Np. When the second
fluence Fp is so set as to fall within the range expressed by
Expression (5) or (6) described above, the post-annealing can be
performed to activate the impurity with no damage at the surface of
the semiconductor substrate 51.
[0177] The first number of radiated pulses Nd and the second number
of radiated pulses Np preferably satisfy Expression (7) below.
2.ltoreq.Nd<Np (7)
[0178] 2.5 Set value of transmittance of light passing through
attenuator
[0179] The value at which the transmittance of light passing
through the attenuator 42 is so set that the fluence of the pulsed
laser light has a predetermined value will next be described.
First, let T be the transmittance of light passing through the
attenuator 42 and T' be the transmittance of light passing along
the optical path from the attenuator 42 to the radiation receiving
object 50. Further, let Et be the pulse energy of the pulsed laser
light incident on the attenuator 42 and F be the fluence of the
pulsed laser light on the surface of the radiation receiving object
50. In this case, the fluence F is expressed by Expression (8)
below.
F=TT'Et/(BxBy) (8)
[0180] For example, it is assumed in Comparative Example that the
transmittance T' is 100%, that is, T'=1. In this case, the
transmittance T of light passing through the attenuator 42 is
expressed by the following Expression (9).
T=(F/Et)(BxBy) (9)
[0181] The laser radiation controller 31 is configured to calculate
the first transmittance Td and the second transmittance Tp
described before by substituting the first fluence Fd and the
second fluence Fp described before into Expression (9) described
above. In a case where the transmittance T' is a fixed value
smaller than 1, the first transmittance Td and the second
transmittance Tp may be calculated based on Expression (10)
below.
T=(F/EtT')(BxBy) (610)
[0182] 2.6 Operation of Laser Radiation System
[0183] 2.6.1 Main Procedure
[0184] FIG. 5 is a flowchart showing processes in laser doping
control and post-annealing control performed by the laser radiation
controller 31. The laser radiation controller 31 is configured to
operate the laser radiation system 2 by carrying out the following
processes.
[0185] When the radiation receiving object 50 is placed on the
table 32 (step S100), the laser radiation controller 31 reads the
first radiation condition for laser doping and the second radiation
condition for post-annealing from the storage (step S110). The
first radiation condition contains the first fluence Fd and the
first number of radiated pulses Nd. The second radiation condition
contains the second fluence Fp and the second number of radiated
pulses Np.
[0186] The laser radiation controller 31 then causes the laser
apparatus 3 to perform adjustment oscillation (step S120). Upon
completion of the adjustment oscillation, the laser radiation
controller 31 controls the XYZ stage 33 to set the irradiated
region A irradiated with the pulsed laser light in the initial
position IP shown in FIG. 3A (step S130). The laser radiation
controller 31 adjusts the XYZ stage 33 in the axis-Z direction in
such a way that the surface of the radiation receiving object 50 is
located in the position to which the transfer optical system 44
transfers the rectangularly shaped beam in the focal plane of the
condenser lens 46 of the beam homogenizer 43 (step S140).
[0187] The laser radiation controller 31 then calculates parameters
for laser doping and the post-annealing (step S150). The parameters
for laser doping include the first transmittance Td of light
passing through the attenuator 42 and the first scan speed Vdx. The
parameters for post-annealing include the second transmittance Tp
of light passing through the attenuator 42 and the second scan
speed Vpx.
[0188] The laser radiation controller 31 sets the parameters for
laser doping in the laser radiation apparatus 4 (step S160). The
laser radiation controller 31 then performs the scan radiation in
which the radiation receiving object 50 is irradiated with the
pulsed laser light while moving the irradiated region A in the
axis-X direction at a fixed speed along the first scan path Sd
described before (step S170). The laser radiation controller 31
evaluates whether or not all the chip formation regions 53 have
been irradiated with the pulsed laser light whenever the scan
radiation corresponding to one row in the axis-X direction is
completed (step S180).
[0189] In a case where all the chip formation regions 53 have not
been irradiated with the pulsed laser light (NO in step S180), the
laser radiation controller 31 moves the irradiated region A in the
axis-Y direction and places the irradiated region A in the scan
radiation start position in the next row (step S190). The laser
radiation controller 31 then returns to the process in step S170
and performs the scan radiation in the axis-X direction. The laser
radiation controller 31 repeats steps S170 to S190 until all the
chip formation regions 53 are irradiated with the pulsed laser
light. In a case where all the chip formation regions 53 have been
irradiated with the pulsed laser light (YES in step S180), the
laser radiation controller 31 terminates the laser doping control
and causes the irradiated region A to return to the initial
position IP (step S200).
[0190] The laser radiation controller 31 then sets the parameters
for the post-annealing in the laser radiation apparatus 4 (step
S210). The laser radiation controller 31 then performs the scan
radiation in which the radiation receiving object 50 is irradiated
with the pulsed laser light while moving the irradiated region A in
the axis-X direction at a fixed speed along the second scan path Sp
described before (step S220). The following steps S230 and S240 are
the same as steps S180 and S190 described above. In a case where
all the chip formation regions 53 have been irradiated with the
pulsed laser light (YES in step S230), the laser radiation
controller 31 terminates the post-annealing control.
[0191] 2.6.2 Details of S110
[0192] FIG. 6 shows a subroutine illustrating the details of the
process of reading the first and second radiation conditions (step
S110) in the main procedure shown in FIG. 5. In step S110, the
laser radiation controller 31 first reads the first fluence Fd and
the first number of radiated pulses Nd as the first radiation
condition from the storage (step S111). The laser radiation
controller 31 then reads the second fluence Fp and the second
number of radiated pulses Np as the second radiation condition from
the storage (step S112). The laser radiation controller 31 then
returns to the processes in the main procedure.
[0193] 2.6.3 Details of S120
[0194] FIG. 7 shows a subroutine illustrating the details of the
process of causing the laser apparatus 3 to perform the adjustment
oscillation (step S120) in the main procedure shown in FIG. 5. In
step S120, the laser radiation controller 31 first transmits the
target pulse energy Et and other data to the laser controller 13
(step S121). For example, the target pulse energy Et is 100 mJ.
[0195] The laser radiation controller 31 then outputs the light
emission trigger Tr at the repetitive frequency f to the laser
controller 13 (step S122). The laser radiation controller 31 then
evaluates whether or not the preparation completion signal Rd has
been received from the laser controller 13 (step S123). When the
laser radiation controller 31 has not received the preparation
completion signal Rd (NO in step S123), the laser radiation
controller 31 returns to step S122. When the laser radiation
controller 31 has received the preparation completion signal Rd
(YES in step S123), the laser radiation controller 31 returns to
the processes in the main procedure. The repetitive frequency f is
substantially equal to the repetitive frequency in the scan
exposure and is, for example, 6000 Hz.
[0196] 2.6.4 Details of S150
[0197] FIG. 8 shows a subroutine illustrating the details of the
process of calculating the parameters for laser doping and
post-annealing (step S150) in the main procedure shown in FIG. 5.
In step S150, the laser radiation controller 31 first uses data on
the first fluence Fd to calculate the first transmittance Td for
laser doping based on Expression (9) described above (step S151).
The laser radiation controller 31 then uses the data on the first
number of radiated pulses Nd, the repetitive frequency f, and the
first beam width Bx to calculate the first scan speed Vdx for laser
doping based on Expression (2) described above (step S152).
[0198] The laser radiation controller 31 then uses data on the
second fluence Fp to calculate the second transmittance Tp for
post-annealing based on Expression(9) described above (step S153).
The laser radiation controller 31 then uses the data on the second
number of radiated pulses Np, the repetitive frequency f, and the
first beam width Bx to calculate the second scan speed Vpx for
post-annealing based on Expression (3) described above (step S154).
The laser radiation controller 31 then returns to the processes in
the main procedure.
[0199] 2.6.5 Details of S160
[0200] FIG. 9 shows a subroutine illustrating the details of the
process of setting the parameters for the laser doping (step S160)
in the main procedure shown in FIG. 5. In step S160, the laser
radiation controller 31 first sets the transmittance of light
passing through the attenuator 42 at the first transmittance Td
calculated in step S151 (step S161). Specifically, the laser
radiation controller 31 sets the rotary stages 42c and 42d provided
in the attenuator 42 in such a way that the transmittance of light
passing through the attenuator 42 is the first transmittance
Td.
[0201] The laser radiation controller 31 then sets the scan
radiation speed at the first scan speed Vdx calculated in step S152
(step S162). Specifically, the laser radiation controller 31 sets
the XYZ stage 33 in such a way that the speed at which the
irradiated region A is moved relative to the radiation receiving
object 50 is the first scan speed Vdx. The laser radiation
controller 31 then returns to the processes in the main
procedure.
[0202] 2.6.6 Details of S210
[0203] FIG. 10 shows a subroutine illustrating the details of the
process of setting the parameters for post-annealing (step S210) in
the main procedure shown in FIG. 5. In step S210, the laser
radiation controller 31 first sets the transmittance of light
passing through the attenuator 42 at the second transmittance Tp
calculated in step S153 (step S211). Specifically, the laser
radiation controller 31 sets the rotary stages 42c and 42d provided
in the attenuator 42 in such a way that the transmittance of light
passing through the attenuator 42 is the second transmittance
Tp.
[0204] The laser radiation controller 31 then sets the scan
radiation speed at the second scan speed Vpx calculated in step
S154 (step S212). Specifically, the laser radiation controller 31
controls the XYZ stage 33 in such a way that the speed at which the
irradiated region A is moved relative to the radiation receiving
object 50 is the second scan speed Vpx. The laser radiation
controller 31 then returns to the processes in the main
procedure.
[0205] 2.6.7 Details of S170
[0206] FIG. 11 shows a subroutine illustrating the details of the
process of performing the scan radiation in the axis-X direction
(step S170) in the main procedure shown in FIG. 5. In step S170,
the laser radiation controller 31 first controls the XYZ stage 33
to cause it to start moving the irradiated region A in the axis-X
direction (step S171). The movement of the irradiated region A
includes accelerated motion, fixed-speed linear motion, and
decelerated motion, and the laser radiation controller 31 sets the
XYZ stage 33 in such a way that the speed of fixed-speed linear
motion is the first scan speed Vdx.
[0207] Upon the start of the movement of the irradiated region A,
the laser radiation controller 31 outputs the light emission
trigger Tr at the repetitive frequency f to the laser controller 13
(step S172). For example, the repetitive frequency f is 6000 Hz.
Until the movement of the irradiated region A in the axis-X
direction is completed (as long as result of step S173 is No), the
laser radiation controller 31 carries out step S172 to output the
light emission trigger Tr to the laser controller 13. Upon the
completion of the movement of the irradiated region A in the axis-X
direction (YES in step S173), the laser radiation controller 31
stops outputting the light emission trigger Tr to the laser
controller 13 (step S174). The laser radiation controller 31 then
returns to the processes in the main procedure.
[0208] The details of step S220 in the main procedure are the same
as the details of step S170 described above and will therefore not
be described.
[0209] 2.7 Problems
[0210] The first fluence Fd appropriate for the laser doping
greatly differs from the second fluence Fp appropriate for the
post-annealing. Therefore, in Comparative Example, the
transmittance T of light passing through the attenuator 42 is so
changed that the fluence in the laser doping differs from the
fluence in the post-annealing. Specifically, since the area S of
the irradiated region A (=BxBy) is fixed, the transmittance T of
light passing through the attenuator 42 is changed to a value
proportional to the fluence F based on Expression (9) or (10)
described above.
[0211] Since the first fluence Fd and the second fluence Fp satisfy
the relationship Fd>Fp, energy corresponding to a ratio
(Td-Tp)/Td is undesirably lost in the attenuator 42 in the
post-annealing with respect to the laser doping. The post-annealing
therefore poses a problem of low use efficiency of the pulse energy
of the pulsed laser light. As described above, when the pulse
energy use efficiency is low in the post-annealing, the scan
radiation requires a long period, resulting in a decrease in
throughput of the laser radiation system.
[0212] In embodiments described below, to solve the problem
described above, a beam homogenizer configured to be capable of
changing the beam width in the direction in which a target object
is scanned with the pulsed laser light is used to change the
fluence of the pulsed laser light.
3. First Embodiment
[0213] 3.1 Configuration
[0214] FIG. 12 schematically shows the configuration of a laser
radiation system 2a according to the first embodiment of the
present disclosure. The laser radiation system 2a according to the
first embodiment includes a laser radiation apparatus 4a in place
of the laser radiation apparatus 4 provided in the laser radiation
system 2 according to Comparative Example. In the following
description, substantially the same portions as the components of
the laser radiation system 2 according to Comparative Example have
the same reference characters and will not be described as
appropriate. The laser radiation system 2a includes the laser
apparatus 3 and the laser radiation apparatus 4a. The laser
apparatus 3 has the same configuration as that of the laser
apparatus 3 in Comparative Example. The laser radiation apparatus
4a includes a beam homogenizer 43a in an optical system 40a in
place of the beam homogenizer 43 in Comparative Example.
[0215] The beam homogenizer 43a includes a first fly-eye lens 45a
for laser doping beam generation, a second fly-eye lens 45b for
post-annealing beam generation, a uniaxial movement stage 47 as a
first actuator, and the condenser lens 46. The first fly-eye lens
45a and the second fly-eye lens 45b are disposed on the uniaxial
movement stage 47. The uniaxial movement stage 47 is configured to
be controlled by a control signal inputted from the laser radiation
controller 31. The laser radiation controller 31 is configured to
control the uniaxial movement stage 47 to selectively place one of
the first fly-eye lens 45a and the second fly-eye lens 45b in the
optical path of the pulsed laser light. That is, the beam
homogenizer 43a is configured to be capable of selectively
generating the beam for laser doping or the beam for
post-annealing.
[0216] FIG. 13A shows the configuration of the first fly-eye lens
45a. FIG. 13B shows the configuration of the second fly-eye lens
45b. The first fly-eye lens 45a and the second fly-eye lens 45b
each have the same configuration as that of the fly-eye lens 45 in
Comparative Example shown in FIG. 2 except that the cylindrical
surfaces are arranged at different intervals.
[0217] A plurality of first cylindrical surfaces 451a, which each
have negative curvature in the axis-V direction and extend in the
axis-H direction, are arranged on a first surface of the first
fly-eye lens 45a in the axis-V direction at first intervals Lv1. A
plurality of second cylindrical surfaces 452a, which each have
negative curvature in the axis-H direction and extend in the axis-V
direction, are arranged on a second surface of the first fly-eye
lens 45a in the axis-H direction at second intervals Lh1. A
plurality of first cylindrical surfaces 451b, which each have
negative curvature in the axis-V direction and extend in the axis-H
direction, are arranged on a first surface of the second fly-eye
lens 45b in the axis-V direction at first intervals Lv2. A
plurality of second cylindrical surfaces 452b, which each have
negative curvature in the axis-H direction and extend in the axis-V
direction, are arranged on a second surface of the second fly-eye
lens 45b in the axis-H direction at second intervals Lh2.
[0218] The intervals Lv1, Lv2, Lh1, and Lh2 satisfy the following
relationships: Lv1<Lh1, Lv2<Lh2, Lv1<Lv2, and Lh1=Lh2. The
first fly-eye lens 45a is disposed in the optical path of the
pulsed laser light in the laser doping. The second fly-eye lens 45b
is disposed in the optical path of the pulsed laser light in the
post-annealing.
[0219] FIG. 14A shows an irradiated region Ad of the radiation
receiving object 50 irradiated with the laser doping beam generated
by the first fly-eye lens 45a. FIG. 14B shows an irradiated region
Ap of the radiation receiving object 50 irradiated with the
post-annealing beam generated by the second fly-eye lens 45b. The
irradiated region Ad has a rectangular shape and has a first beam
width Bdx in the axis-X direction and a second beam width Bdy in
the axis-Y direction. The irradiated region Ap has a rectangular
shape and has a first beam width Bpx in the axis-X direction and a
second beam width Bpy in the axis-Y direction.
[0220] The beam widths Bdx, Bdy, Bpx, and Bpy satisfy the following
relationships: Bdx<Bdy, Bpx<Bpy, Bdx<Bpx, and Bdy=Bpy. The
second beam widths Bdy and Bpy are equal to the first beam width By
in Comparative Example and satisfy Expression (1) described
above.
[0221] 3.2 Operation of laser radiation system
[0222] 3.2.1 Main procedure
[0223] FIGS. 15 and 16 are flowchart showing processes in the laser
doping control and the post-annealing control performed by the
laser radiation controller 31. The laser radiation controller 31 is
configured to operate the laser radiation system 2a by carrying out
the following processes.
[0224] Steps S300 to S350 in the present embodiment are the same as
steps S100 to S150 in Comparative Example. In the present
embodiment, the laser radiation controller 31 sets the parameters
for laser doping in the laser radiation apparatus 4a (step S360)
after step S350. The laser radiation controller 31 then switches
the first beam width of the pulsed laser light in the axis-X
direction with which the radiation receiving object 50 is
irradiated to the first beam width Bdx (step S370). The first beam
width is thus set at the first beam width Bdx for laser doping. The
following steps S380 to S410 are the same as steps S170 to S200 in
Comparative Example.
[0225] In the present embodiment, the laser radiation controller 31
sets the parameters for post-annealing in the laser radiation
apparatus 4a (step S420) after step S410. The laser radiation
controller 31 then switches the first beam width of the pulsed
laser light in the axis-X direction with which the radiation
receiving object 50 is irradiated to the first beam width Bpx (step
S430). The first beam width is thus set at the first beam width Bpx
for post-annealing. The following steps S440 to S460 are the same
as steps S220 to S240 in Comparative Example.
[0226] 3.2.2 Details of S350
[0227] FIG. 17 shows a subroutine illustrating the details of the
process of calculating the parameters for laser doping and
post-annealing (step S350) in the main procedure shown in FIG. 15.
In step S350, the laser radiation controller 31 first uses the data
on the first fluence Fd to calculate the first transmittance Td of
light passing through the attenuator 42 for laser doping based on
Expression (11) below (step S351).
Td=(Fd/Et)(BdxBdy) (11)
[0228] The laser radiation controller 31 then uses the data on the
first number of radiated pulses Nd, the repetitive frequency f, and
the first beam width Bdx to calculate the first scan speed Vdx for
laser doping based on Expression (12) below (step S352).
Vdx=fBdx/Nd (12)
[0229] The laser radiation controller 31 then uses the data on the
second fluence Fp to calculate the second transmittance Tp of light
passing through the attenuator 42 for post-annealing based on
Expression (13) below (step S353). It is noted that Bdy=Bpy.
Tp=(Fp/Et)(BpxBpy) (13)
[0230] The laser radiation controller 31 then uses the data on the
second number of radiated pulses Np, the repetitive frequency f,
and the first beam width Bpx to calculate the second scan speed Vpx
for post-annealing based on Expression (14) below (step S354).
Vpx=fBpx/Np (14)
[0231] The laser radiation controller 31 then returns to the
processes in the main procedure.
[0232] 3.2.3 Details of S360
[0233] FIG. 18 shows a subroutine illustrating the details of the
process of setting the parameters for the laser doping (step S360)
in the main procedure shown in FIG. 15. Steps S361 and S362 are the
same as steps S161 and S162 in Comparative Example. After step
S362, the laser radiation controller 31 sets a flag FL in such a
way that FL=FLd is satisfied (step S363). The laser radiation
controller 31 then returns to the processes in the main
procedure.
[0234] 3.2.4 Details of S420
[0235] FIG. 19 shows a subroutine illustrating the details of the
process of setting the parameters for post-annealing (step S420) in
the main procedure shown in FIG. 16. Steps S421 and S422 are the
same as steps S211 and S212 in Comparative Example. After step
S422, the laser radiation controller 31 sets the flag FL in such a
way that FL=FLp is satisfied (step S423). The laser radiation
controller 31 then returns to the processes in the main
procedure.
[0236] 3.2.5 Details of S370
[0237] FIG. 20 shows a subroutine illustrating the details of the
process of switching the first beam width to the other (step S370)
in the main procedure shown in FIG. 16. In step S370, the laser
radiation controller 31 first evaluates whether or not the flag FL
is FLd (step S371). When FL=FLd is satisfied (YES in step S371),
the laser radiation controller 31 controls the uniaxial movement
stage 47 to place the first fly-eye lens 45a in the optical path of
the pulsed laser light (step S372). The irradiated region Ad shown
in FIG. 14A is thus the irradiated region irradiated with the
pulsed laser light.
[0238] On the other hand, when FL=FLd is not satisfied (NO in step
S371), the laser radiation controller 31 controls the uniaxial
movement stage 47 to place the second fly-eye lens 45b in the
optical path of the pulsed laser light (step S373). The irradiated
region Ap shown in FIG. 14B is thus the irradiated region
irradiated with the pulsed laser light. The laser radiation
controller 31 then returns to the processes in the main
procedure.
[0239] The details of step S430 in the main procedure are the same
as the details of step S370 described above and will therefore not
be described.
[0240] 3.3 Effects
[0241] In the present embodiment, the first fly-eye lens 45a and
the second fly-eye lens 45b are preferably so configured that the
first intervals Lv1 and Lv2 satisfy Expression (15) below.
Lv1/Lv2=Fp/Fd (15)
[0242] In this case, the first beam width Bdx for laser doping and
a first beam width Bpx for post-annealing satisfy Expression (16)
below.
BdxFd=BpxFp (16)
[0243] As a result, when Expression (15) described above is
substantially satisfied, the second transmittance Tp for
post-annealing calculated in step S353 is substantially equal to
the first transmittance Td for laser doping calculated in step
S351.
[0244] As described above, in the present embodiment, the
transmittance of light passing through the attenuator 42 in the
laser doping is substantially equal to that in the post-annealing,
whereby energy loss in the post-annealing with respect to the laser
doping is suppressed. Therefore, in the present embodiment, the use
efficiency of the pulse energy of the pulsed laser light is
improved and the period required for the scan radiation is
shortened, whereby the throughput of the laser radiation system is
improved, as compared with those in Comparative Example.
[0245] In the first embodiment, the first fly-eye lens 45a and the
second fly-eye lens 45b each have concave cylindrical surfaces, but
not necessarily, and may each instead have convex cylindrical
surfaces. The fly-eye lenses may still instead be each formed of a
Fresnel lens having the same optical characteristics of cylindrical
lenses and formed on a substrate.
[0246] In the first embodiment, the first fly-eye lens 45a and the
second fly-eye lens 45b are each an integrated optical element, and
the fly-eye lenses may instead each be formed of two cylindrical
arrays. In this case, the two cylindrical arrays may be so disposed
that the directions in which the cylindrical surfaces are arranged
are perpendicular to each other.
4. Second Embodiment
[0247] 4.1 Configuration
[0248] FIG. 21 schematically shows the configuration of a laser
radiation system 2b according to a second embodiment of the present
disclosure. The laser radiation system 2b according to the second
embodiment includes a laser radiation apparatus 4b in place of the
laser radiation apparatus 4a provided in the laser radiation system
2a according to the first embodiment. In the following description,
substantially the same portions as the components of the laser
radiation system 2a according to the first embodiment have the same
reference characters and will not be described as appropriate.
[0249] The laser radiation system 2b includes the laser apparatus 3
and the laser radiation apparatus 4b. The laser apparatus 3 has the
same configuration as that of the laser apparatus 3 in the first
embodiment. In FIG. 21, the laser apparatus 3 is omitted. The laser
radiation apparatus 4b includes a beam homogenizer 43b in an
optical system 40b in place of the beam homogenizer 43 in
Comparative Example. In the present embodiment, the optical system
40b does not include the attenuator 42.
[0250] The beam homogenizer 43b includes a cylindrical lens group
48 and a uniaxial movement stage 49 as a second actuator in place
of the first fly-eye lens 45a, the second fly-eye lens 45b, and the
uniaxial movement stage 47 in the first embodiment. The cylindrical
lens group 48 forms a fly-eye lens.
[0251] FIGS. 22A and 22B show the configuration of the beam
homogenizer 43b in detail. FIG. 22A shows the beam homogenizer 43b
viewed along the axis-H direction. FIG. 22B shows the beam
homogenizer 43b viewed along the axis-V direction. The cylindrical
lens group 48 includes a first cylindrical lens array 48a, a second
cylindrical lens array 48b, and a third cylindrical lens array 48c.
The first cylindrical lens array 48a, the second cylindrical lens
array 48b, and the third cylindrical lens array 48c, and the
condenser lens 46 are disposed in the optical path of the pulsed
laser light in the presented order from the side on the upstream of
the optical path.
[0252] The first cylindrical lens array 48a has a plurality of
convex cylindrical surfaces 481a, which each have predetermined
radius of curvature in the axis-V direction and extend in the
axis-H direction, arranged at the first intervals Lv in the axis-V
direction. The second cylindrical lens array 48b has a plurality of
convex cylindrical surfaces 482a, which each have predetermined
radius of curvature in the axis-V direction and extend in the
axis-H direction, arranged at the first intervals Lv in the axis-V
direction. The first cylindrical lens array 48a and the second
cylindrical lens array 48b have the same configuration and are so
disposed that the flat surfaces of the two lens arrays face each
other.
[0253] The uniaxial movement stage 49 is configured to move the
first cylindrical lens array 48a in the axis-I direction based on a
control signal inputted from the laser radiation controller 31.
Moving the first cylindrical lens array 48a in the axis-I direction
changes the gap D between the first cylindrical lens array 48a and
the second cylindrical lens array 48b.
[0254] The third cylindrical lens array 48c has a plurality of
concave cylindrical surfaces 481c, which each have predetermined
radius of curvature in the axis-H direction and extend in the
axis-V direction, arranged at the second intervals Lh in the axis-H
direction. The third cylindrical lens array 48c is so disposed that
the cylindrical surfaces 481c face the second cylindrical lens
array 48b.
[0255] The second interval Lh is so set that a beam width ILh of
the pulsed laser light in the axis-H direction in a focal plane Pf
of the condenser lens 46 satisfies Expression (17) below.
By=MILh (17)
[0256] In Expression (17), M represents the transfer magnification
provided by the transfer optical system 44. Reference character By
represents the width of the irradiated region A shown in FIG. 3 in
the axis-X direction, that is, the second beam width and satisfies
Expression (1) described above.
[0257] 4.2 Method for setting second beam width
[0258] A method for setting the width of the irradiated region A
shown in FIG. 3 in the axis-X direction, that is, the first beam
width Bx will next be described. In the present embodiment, a beam
width ILv of the pulsed laser light in the axis-V direction in the
focal plane Pf of the condenser lens 46 changes in accordance with
the value of the gap D. A gap Dw, which minimizes the beam width
ILv, is expressed by Expression (18) below.
Dw.apprxeq.Fb1+Ff2 (18)
[0259] In Expression (18), Fb1 represents the back focal length of
the first cylindrical lens array 48a, and Ff2 represents the front
focal length of the second cylindrical lens array 48b.
[0260] The laser radiation controller 31 is configured to control
the uniaxial movement stage 49 to change the gap D over the range
expressed by Expression (19) below, whereby the beam width ILv can
be continuously changed.
Ff2<D<Fb1+Ff2 (19)
[0261] The first beam width Bx and the beam width ILv relate to
each other in the relationship expressed by Expression (20) below,
whereby changing the gap D allows control of the first beam width
Bx.
Bx=MILv (20)
[0262] In Expression (20), the first beam width Bx is the width of
the irradiated region A shown in FIG. 3 in the axis-X
direction.
[0263] The laser radiation controller 31 is configured to store in
advance a function D=f(Bx) or data representing the correspondence
between the gap D and the first beam width Bx. The laser radiation
controller 31 is configured to control the uniaxial movement stage
49 based on the correspondence to adjust the gap D to set the first
beam width Bx at a desired value.
[0264] 4.3 Operation of Laser Radiation System
[0265] 4.3.1 Main Procedure
[0266] The main procedure according to the present embodiment is
the same as that in FIGS. 15 and 16 shown in the first embodiment.
Only steps different from those in the first embodiment will be
described in detail. In the present embodiment, the details of
steps S350, S360, S370, S420, and S430 in the main procedure shown
in FIGS. 15 and 16 differ from those in the first embodiment. Steps
S350', S360', S370', S420', and S430' different from steps S350,
S360, S370, S420, and S430 in the first embodiment will be
described below in detail.
[0267] 4.3.2 Details of S350'
[0268] FIG. 23 shows a subroutine illustrating the details of the
process of calculating the parameters for laser doping and
post-annealing (step S350') in the present embodiment. In step
S350', the laser radiation controller 31 first uses the data on the
first fluence Fd to calculate the first beam width Bdx for laser
doping based on Expression (21) below (step S351').
Bdx=Et/(FdBy) (21)
[0269] Expression (21) described above is based on Expression (11)
described before. In the present embodiment, since the attenuator
42 is not provided, it is assumed that Td=1 and Bdy=By.
[0270] The laser radiation controller 31 then uses the data on the
first number of radiated pulses Nd, the repetitive frequency f, and
the first beam width Bdx to calculate the first scan speed Vdx for
laser doping based on Expression (12) described before (step
S352').
[0271] The laser radiation controller 31 then uses the data on the
second fluence Fp to calculate the first beam width Bpx for
post-annealing based on Expression (22) below (step S353').
Bpx=Et/(FpBy) (22)
[0272] Expression (22) described above is based on Expression (13)
described before. In the present embodiment, since the attenuator
42 is not provided, it is assumed that Tp=1 and Bpy=By.
[0273] The laser radiation controller 31 then uses the data on the
second number of radiated pulses Np, the repetitive frequency f,
and the first beam width Bpx to calculate the second scan speed Vpx
for post-annealing based on Expression (14) described before (step
S354'). The laser radiation controller 31 then returns to the
processes in the main procedure.
[0274] 4.3.3 Details of S360'
[0275] FIG. 24 shows a subroutine illustrating the details of the
process of setting the parameters for the laser doping (step S360')
in the present embodiment. In step S360', the laser radiation
controller 31 first sets the first beam width Bx at the irradiated
region A at the first beam width Bdx for laser doping (step S361').
The laser radiation controller 31 then sets the scan radiation
speed at the first scan speed Vdx calculated in step S352' (step
S362'). The laser radiation controller 31 then returns to the
processes in the main procedure.
[0276] 4.3.4 Details of S420'
[0277] FIG. 25 shows a subroutine illustrating the details of the
process of setting the parameters for post-annealing (step S420')
in the present embodiment. In step S420', the laser radiation
controller 31 first sets the first beam width Bx at the irradiated
region A at the first beam width Bpx for post-annealing (step
S421'). The laser radiation controller 31 then sets the scan
radiation speed at the second scan speed Vpx calculated in step
S354' (step S422'). The laser radiation controller 31 then returns
to the processes in the main procedure.
[0278] 4.3.5 Details of S370'
[0279] FIG. 26 shows a subroutine illustrating the details of the
process of switching the first beam width to the other (step S370')
in the present embodiment. The laser radiation controller 31
controls the uniaxial movement stage 49 to set the gap D at a value
corresponding to the first beam width Bdx for laser doping set in
step S361' (step S371'). The laser radiation controller 31 then
returns to the processes in the main procedure. The details of step
S430' in the main procedure are the same as the details of step
S430 described above and will therefore not be described.
[0280] 4.4 Effects
[0281] In the present embodiment, since the first beam width in the
scan radiation direction is continuously changeable, the fluence of
the pulsed laser light can be precisely controlled. The first
fluence Fd for laser doping and the second fluence Fp for
post-annealing that satisfy Expression (16) described before can be
precisely set without use of any attenuator. Therefore, in the
present embodiment, the use efficiency of the pulse energy of the
pulsed laser light is further improved and the period required for
the scan radiation is shortened, whereby the throughput of the
laser radiation system is further improved.
[0282] In the present embodiment, the cylindrical surfaces 481c of
the third cylindrical array 48c each have a concave shape, but not
necessarily, and can have a convex shape.
[0283] The first cylindrical lens array 48a and the second
cylindrical lens array 48b may each be a single cylindrical lens.
Also in this case, controlling the gap between the pair of
cylindrical lenses allows adjustment of the beam width ILv.
[0284] Table 1 below shows a specific example of the parameters in
the laser doping and the post-annealing in the second embodiment in
the case where Et=100 mJ. Table 2 below shows a specific example of
the parameters in the laser doping and the post-annealing in the
second embodiment in the case where Et=40 mJ.
TABLE-US-00001 TABLE 1 Laser doping Post-Annealing Et 100 mJ Et 100
mJ f 6000 Hz f 6000 Hz Bdy 10 mm Bpy 10 mm Nd 10 pulses Np 100
pulses Fd 6 J/cm.sup.2 Fp 4 J/cm.sup.2 Bdx 0.17 mm Bpx 0.25 mm Vdx
100 mm/s Vpx 15 mm/s
TABLE-US-00002 TABLE 2 Laser doping Post-Annealing Et 40 mJ Et 40
mJ f 4000 Hz f 4000 Hz Bdy 10 mm Bpy 10 mm Nd 10 pulses Np 100
pulses Fd 6 J/cm.sup.2 Fp 4 J/cm.sup.2 Bdx 0.07 mm Bpx 0.1 mm Vdx
26.7 mm/s Vpx 4 mm/s
[0285] Tables 1 and 2 show that the laser doping and the
post-annealing can be performed in the present embodiment even when
the pulsed laser light has low pulse energy, such as 100 mJ or 40
mJ. The fluence Fd in the laser doping and the fluence Fp in the
post-annealing are settable by adjustment of the beam width Bdx in
the scan radiation direction, as described above. The values of the
beam width Bdx in Tables 1 and 2 are adequately adjustable values.
Further, the number of radiated pulses Nd in the laser doping and
the number of radiated pulses Nd in the post-annealing can be
settable by adjustment of the scan speeds Vdx and Vpx,
respectively. The scan speeds Vdx and Vpx in Tables 1 and 2 are
adequately adjustable values.
5. First Variation
[0286] A first variation will next be described. In the first and
second embodiments, the scan radiation for laser doping is
performed on all the irradiated regions A of the radiation
receiving object 50, and then the scan radiation for post-annealing
is performed on the irradiated regions A. Instead, the scan
radiation for laser doping and the scan radiation for
post-annealing can be alternately performed. Variations of the scan
radiation control in the first and second embodiments will be
described below.
[0287] 5.1 Scan Radiation Control
[0288] FIG. 27 shows a first scan path Sd' in the laser doping and
a second scan path Sp' in the post-scanning in the present
variation. The first scan path Sd' extends toward the positive side
of the axis-X direction. The second scan path Sp' extends toward
the negative side of the axis-X direction. That is, in the laser
doping, the irradiated region Ad moves toward the positive side of
the axis X direction relative to the radiation receiving object 50.
On the other hand, in the post-annealing, the irradiated region Ap
moves toward the negative side of the axis-X direction relative to
the radiation receiving object 50. The irradiated region Ad and the
irradiated region Ap have the shapes shown in FIG. 14B.
[0289] Before starting the laser doping, the laser radiation
controller 31 is configured to set the irradiated region Ad in the
initial position IP in the vicinity of a first chip formation
region 53f, which is located in an end portion of the first row and
starts the scan radiation toward the positive side of the axis-X
direction at the first scan speed Vdx along the first scan path
Sd'. When the irradiated region Ad passes through a second chip
formation region 53g located at the last end of the first row, the
laser radiation controller 31 switches the first beam width to the
other width and sets the irradiated region Ap in the vicinity of
the second chip formation region 53g. The laser radiation
controller 31 is thereafter configured to perform the scan
radiation from the second chip formation region 53g toward the
negative side of the axis-X direction at the second scan speed
Vpx.
[0290] When the irradiated region Ap passes through the first chip
formation region 53f, the laser radiation controller 31 moves the
irradiated region Ap toward the positive side of the axis-Y
direction by one row. The laser radiation controller 31 is
thereafter configured to switch the first beam width to the other
and sets the irradiated region Ad in the vicinity of a third chip
formation region 53h. The laser radiation controller 31 is
configured to repeatedly perform the scan radiation described
above, and when the irradiated region Ap passes through a fourth
chip formation region 53i located in an end portion of the last
row, the laser radiation controller 31 causes the irradiated region
Ap to return to the initial position IP. The laser radiation
controller 31 is thereafter configured to terminate the scan
radiation control. The radiation receiving object 50 may then be
replaced with a new radiation receiving object 50.
[0291] 5.2 Operation of Laser Radiation System
[0292] FIG. 28 is a flowchart showing the processes in the laser
doping control and the post-annealing control performed by the
laser radiation controller 31. Steps S500 to S570 in the present
embodiment are the same as steps S300 to S370 in the first
embodiment. In the present embodiment, the parameters for laser
doping are set in step S560, and the first beam width is switched
to the first beam width Bdx for laser doping in step S570. The
laser radiation controller 31 then performs the scan radiation
corresponding to one row toward the positive side of the axis-X
direction at the first scan speed Vdx (step S580).
[0293] When the scan radiation corresponding to one row toward the
positive side of the axis-X direction is completed, the laser
radiation controller 31 sets the parameters for post-annealing in
the laser radiation apparatus 4b (step S590). The laser radiation
controller 31 then switches the first beam width to the first beam
width Bpx for post-annealing (step S600) and performs the scan
radiation corresponding to one row toward the negative side of the
axis-X direction at the second scan speed Vpx (step S610). Whenever
the scan radiation corresponding to one row toward any of the
positive and negative sides of the axis-X direction is completed,
the laser radiation controller 31 evaluates whether or not all the
chip formation regions 53 have been irradiated (step S620).
[0294] In a case where all the chip formation regions 53 have not
been irradiated (NO in step S620), the laser radiation controller
31 moves the irradiated region in the axis-Y direction and sets the
irradiated region in the scan radiation start position in the next
row (step S630). The laser radiation controller 31 then returns to
the process in step S560 and repeatedly carries out the same
processes described above. In a case where all the chip formation
regions 53 have been irradiated (YES in step S620), the laser
radiation controller 31 terminates the scan radiation control.
[0295] 5.3 Effects
[0296] In the scan radiation control according to the present
variation, in which the distance over which the XYZ stage 33 is
moved in the axis-Y direction is shortened as compared with those
according to the first and second embodiments, the throughput of
the laser radiation system is further improved. Further, since the
scan radiation for laser doping and the scan radiation for
post-annealing are continuously performed on a row basis, the
irradiated region in the laser doping and the irradiated region in
the post-annealing coincide with each other in the axis-Y direction
with improved precision.
6. Second Variation
[0297] A second variation will next be described. In the first
embodiment, the beam homogenizer 43a is disposed in the optical
path between the high-reflectance mirrors 41b and 41c, as shown in
FIG. 3, but the position where the beam homogenizer 43a is disposed
in not limited thereto.
[0298] FIG. 29 schematically shows the configuration of a laser
radiation system 2c according to the present variation. The
configuration of the laser radiation system 2c differs from the
configuration of the laser radiation system 2 according to the
first embodiment only in terms of the configuration of an optical
system 40c provided in a laser radiation apparatus 4c. In the
optical system 40c, the beam homogenizer 43a is disposed in the
optical path between the high-reflectance mirror 41c and the window
36, unlike in the transfer optical system 44 described before.
[0299] The beam homogenizer 43a includes the first fly-eye lens
45a, the second fly-eye lens 45b, the uniaxial movement stage 47,
and the condenser lens 46, as in the first embodiment. The laser
radiation controller 31 is configured to control the uniaxial
movement stage 47 to insert one of the first fly-eye lens 45a and
the second fly-eye lens 45b into the optical path of the pulsed
laser light. In the present variation, the condenser lens 46 is so
disposed that the focal plane thereof coincides with the surface of
the radiation receiving object 50. The condenser lens 46
illuminates the surface of the radiation receiving object 50 with
the pulsed laser light in the form of Koehler illumination.
[0300] The other configurations of the laser radiation system 2c
according to the present variation are the same as those of the
laser radiation system 2 according to the first embodiment.
[0301] Further, the beam homogenizer 43b described in the second
embodiment may be disposed in the optical path between the
high-reflectance mirror 41c and the window 36 in place of the
transfer optical system 44, as in the present variation.
7. Third Embodiment
[0302] 7.1 Configuration
[0303] FIG. 30 schematically shows the configuration of a laser
radiation system 2d according to a third embodiment of the present
disclosure. The laser radiation system 2d according to the third
embodiment includes a laser radiation apparatus 4d in place of the
laser radiation apparatus 4b provided in the laser radiation system
2b according to the second embodiment. In the following
description, substantially the same portions as the components of
the laser radiation system 2b according to the second embodiment
have the same reference characters and will not be described as
appropriate.
[0304] The laser radiation system 2d includes the laser apparatus 3
and the laser radiation apparatus 4d. The laser apparatus 3 has the
same configuration as that of the laser apparatus 3 in the first
embodiment. The laser radiation apparatus 4d includes a reflectance
variable beam splitter 60 disposed in the optical path between the
high-reflectance mirrors 41a and 41b in an optical system 40d. The
optical system 40d includes a first beam homogenizer 70 for laser
doping and a second beam homogenizer 80 for post-annealing in place
of the beam homogenizer 43b in the second embodiment. FIG. 31 shows
the configuration of the reflectance variable beam splitter 60.
[0305] FIG. 31 shows the reflectance variable beam splitter 60
viewed along the direction labeled with the arrow a in FIG. 32,
which will be described later. The reflectance variable beam
splitter 60 is formed of a partial reflection mirror 61, a holder
61a, and a uniaxial movement stage 62. The partial reflectance
mirror 61 has an oblong shape and has reflectance that monotonously
decreases along the axis-H direction, which is the longitudinal
direction of the partial reflection mirror 61. The holder 61a is
configured to hold an outer edge portion of the partial reflection
mirror 61. The uniaxial movement stage 62 is configured to engage
with the holder 61a and move the partial reflection mirror 61 in
the axis-H direction based on a control signal inputted from the
laser radiation controller 31.
[0306] Reference character 63 represents a light incident region on
which the pulsed laser light incident on the partial reflection
mirror 61 from the laser apparatus 3 via the optical path tube 5
and the high-reflectance mirror 41a is incident. The position of
the light incident region 63 changes when the uniaxial movement
stage 62 is driven to move the partial reflection mirror 61 in the
axis-H direction. That is, moving the partial reflection mirror 61
in the axis-H direction changes reflectance R of light reflected
off the light incident region 63. The partial reflection mirror 61
is configured to transmit part of the pulsed laser light incident
on the light incident region 63 and reflect another part of the
pulsed laser light.
[0307] FIG. 32 shows the configuration of the first beam
homogenizer 70 and the second beam homogenizer 80. The first beam
homogenizer 70 is disposed in the optical path of the transmitted
light passing through the partial reflection mirror 61. The
transmitted light is reflected off the high-reflectance mirror 41b
and enters the first beam homogenizer 70. The second beam
homogenizer 80 is disposed in the optical path of the reflected
light reflected off the partial reflection mirror 61.
[0308] Assuming that the pulsed laser light incident on the partial
reflection mirror 61 has the pulse energy Et, the pulsed laser
light that enters the first beam homogenizer 70 has pulse energy
(1-R)Et. The pulsed laser light that enters the second beam
homogenizer 80 has pulse energy REt.
[0309] The first beam homogenizer 70 includes a cylindrical lens
group 71, a condenser lens 72, and a uniaxial movement stage 73 as
a third actuator. The cylindrical lens group 71 forms a fly-eye
lens. The cylindrical lens group 71 includes a first cylindrical
lens array 71a, a second cylindrical lens array 71b, and a third
cylindrical lens array 71c. The configuration of the first beam
homogenizer 70 is the same as the configuration of the beam
homogenizer 43b in the second embodiment.
[0310] The uniaxial movement stage 73 moves the first cylindrical
lens array 71a in the axis-I direction to change the gap Dd between
the first cylindrical lens array 71a and the second cylindrical
lens array 71b. Changing the gap Dd allows control of a beam width
ILvd of the pulsed laser light in the axis-V direction in a focal
plane Pf of the condenser lens 72.
[0311] Reference character Ad shown in FIGS. 33A and 33B represents
the beam shape of the pulsed laser light which travels from the
first beam homogenizer 70 via the high-reflectance mirror 41c and
the transfer optical system 44 and with which the radiation
receiving object 50 is irradiated, that is, the irradiated region.
The first beam width Bdx, which is the width of the irradiated
region Ad in the axis-X direction, and the beam width ILvd relate
to each other in the relationship expressed by Expression (23)
below.
Bdx=MILvd (23)
[0312] The first beam width Bdx for laser doping can therefore be
controlled by changing the gap Dd.
[0313] The second beam homogenizer 80 includes a cylindrical lens
group 81, a condenser lens 82, and a uniaxial movement stage 83 as
a fourth actuator. The cylindrical lens group 81 forms a fly-eye
lens. The cylindrical lens group 81 includes a fourth cylindrical
lens array 81a, a fifth cylindrical lens array 81b, and a sixth
cylindrical lens array 81c. The configuration of the second beam
homogenizer 80 is the same as the configuration of the beam
homogenizer 43b in the second embodiment.
[0314] The uniaxial movement stage 83 moves the fourth cylindrical
lens array 81a in the axis-I direction to change the gap Dp between
the fourth cylindrical lens array 81a and the fifth cylindrical
lens array 81b. Changing the gap Dp allows control of a beam width
ILvp of the pulsed laser light in the axis-V direction in a focal
plane Pf of the condenser lens 82.
[0315] Reference character Ap shown in FIGS. 33A and 33B represents
the beam shape of the pulsed laser light which travels from the
second beam homogenizer 80 via the high-reflectance mirror 41c and
the transfer optical system 44 and with which the radiation
receiving object 50 is irradiated, that is, the irradiated region.
The first beam width Bpx, which is the width of the irradiated
region Ap in the axis-X direction, and the beam width ILvp relate
to each other in the relationship expressed by Expression (24)
below.
Bpx=MILvp (24)
[0316] The first beam width Bpx for post-annealing can therefore be
controlled by changing the gap Dp.
[0317] The irradiated region Ad and the irradiated region Ap have
the same width in the axis-Y direction, that is, the second beam
width By.
[0318] 7.2 Scan Radiation Control
[0319] Scan radiation control performed by the laser radiation
controller 31 in the present embodiment will next be described. In
the present embodiment, the XYZ stage 33 moves the radiation
receiving object 50 at a fixed speed with the irradiated region Ad
irradiated with the pulsed laser light for laser doping and the
irradiated region Ap irradiated with the pulsed laser light for
post-annealing. That is, in the present embodiment, the scan
radiation using the beam for laser doping and the scan radiation
using the beam for post-annealing are simultaneously performed.
[0320] Specifically, the irradiated region Ad for laser doping and
the irradiated region Ap for post-annealing are so set on the
surface of the radiation receiving object 50 as to be adjacent to
each other in the axis-X direction. The irradiated region Ad is
shifted from the irradiated region Ap toward the front side of the
scan direction. That is, the laser radiation controller 31 is
configured to control the XYZ stage 33 to linearly move the
radiation receiving object 50 at a fixed scan speed Vx in such a
way that the irradiated region Ad passes through each of the chip
formation regions 53 before the irradiated region Ap. The laser
radiation controller 31 is configured to perform the scan radiation
on a row basis toward the positive side of the axis-X direction
and, whenever one-row scan radiation ends, further configured to
stop the radiation of the pulsed laser light and cause the
irradiated region to return to the front end of the row. In FIG.
33A, reference character Sdp represents the path of the scan
radiation. Reference character Soff represents the path where the
radiation of the pulsed laser light is stopped and along which the
XYZ stage 33 is moved.
[0321] 7.3 Method for Setting Reflectance
[0322] A method for setting the reflectance R of light reflected
off the light incident region 63 based on the first and second
radiation conditions will next be described. In the present
embodiment, the fluence Fd in the laser doping is expressed by
Expression (25) below. The fluence Fp in the post-annealing is
expressed by Expression (26) below.
Fd=(1-R)Et/(BdxBy) (25)
Fp=REt/(BpxBy) (26)
[0323] Expression (27) below is derived from Expressions (25) and
(26) described above.
.alpha.=Fp/Fd=(R/(1-R))(Bdx/Bpx) (27)
[0324] In the present embodiment, since the same scan speed is used
in both the laser doping and the post-annealing, that is,
Vx=Vdx=Vpx, Expression (28) below is derived from Expressions (12)
and (14) described before.
.beta.=Np/Nd=Bpx/Bdx (28)
[0325] Expression (29) below is derived from Expressions (27) and
(28) described above.
R=.alpha..beta./(1+.beta.) (29)
[0326] The reflectance R can therefore be calculated based on
Expressions (27) to (29) described above by using the first fluence
Fd and the first number of radiated pulses Nd contained in the
first radiation condition and the second fluence Fp and the second
number of radiated pulses Np contained in the second radiation
condition.
[0327] The laser radiation controller 31 is configured to set the
reflectance R by driving the uniaxial movement stage 62 provided in
the reflectance variable beam splitter 60 to move the partial
reflection mirror 61 to a position where the reflectance R of light
reflected off the light incident region 63 is the value calculated
as described above.
[0328] 7.4 Operation of Laser Radiation System
[0329] 7.4.1 Main Procedure
[0330] FIG. 34 is a flowchart showing the processes in the laser
doping control and the post-annealing control performed by the
laser radiation controller 31. Steps S700 to S740 in the present
embodiment are the same as steps S300 to S340 in the first
embodiment. In the present embodiment, the laser radiation
controller 31 is configured to calculate the parameters for laser
doping and post-annealing after step S740 (step S750) and set the
calculated parameters in the laser radiation apparatus 4d (step
S760).
[0331] The laser radiation controller 31 then performs the scan
radiation in which the radiation receiving object 50 is irradiated
with the pulsed laser light while moving both the irradiated
regions Ad and Ap toward the positive side of the axis-X direction
at a fixed speed along a scan path Sdp (step S770). When the scan
radiation corresponding to one row toward the positive side of the
axis-X direction is completed, the laser radiation controller 31
moves the irradiated regions Ad and Ap toward the negative side of
the axis-X direction along the path Soff (step S780).
[0332] The laser radiation controller 31 then evaluates whether or
not all the chip formation regions 53 have been irradiated (step
S790). In a case where all the chip formation regions 53 have not
been irradiated (NO in step S790), the laser radiation controller
31 moves the irradiated regions Ad and Ap in the axis-Y direction
and sets the irradiated regions in the scan radiation start
position in the next row (step S800). The laser radiation
controller 31 then returns to the process in step S770 and
repeatedly carries out the same processes described above. In a
case where all the chip formation regions 53 have been irradiated
(YES in step S790), the laser radiation controller 31 terminates
the scan radiation control.
[0333] 7.4.2 Details of S750
[0334] FIG. 35 shows a subroutine illustrating the details of the
process of calculating the parameters for laser doping and
post-annealing (step S750) in the main procedure shown in FIG. 34.
In step S750, the laser radiation controller 31 first calculates
the ratio a between the first fluence Fd and the second fluence Fp
and the ratio 13 between the first number of radiated pulses Nd and
the second number of radiated pulses Np (step S751). The laser
radiation controller 31 then calculates the reflectance R based on
Expression (29) described above (step S752).
[0335] The laser radiation controller 31 then calculates the first
beam width Bdx for laser doping based on Expression (30) below
(step S753), which is the deformation of Expression (25) described
above.
Bdx=(1-R)Et/(FdBy) (30)
[0336] The laser radiation controller 31 further calculates the
first beam width Bpx for post-annealing based on Expression (31)
below (step S754), which is the deformation of Expression (26)
described above.
Bpx=REt/(FpBy) (31)
[0337] The laser radiation controller 31 then calculates the scan
speed Vx based on Expression (32) below (step S755).
Vx=fBdx/Nd (32)
[0338] The laser radiation controller 31 then returns to the
processes in the main procedure.
[0339] 7.4.3 Details of S760
[0340] FIG. 36 shows a subroutine illustrating the details of the
process of setting the parameters for laser doping and
post-annealing (step S760) in the main procedure shown in FIG. 34.
In step S760, the laser radiation controller 31 first controls the
uniaxial movement stage 62 provided in the reflectance variable
beam splitter 60 to move the partial reflection mirror 61 to a
position where the reflectance R of light reflected off the light
incident region 63 is the value calculated in step S752 (step
S761).
[0341] The laser radiation controller 31 then controls the uniaxial
movement stage 73 provided in the first beam homogenizer 70 to set
the gap Dd in such a way that the gap Dd corresponds to the
calculated value of the first beam width Bdx calculated in step
S753 (step S762). The laser radiation controller 31 further
controls the uniaxial movement stage 83 provided in the second beam
homogenizer 80 to set the gap Dp in such a way that the gap Dp
corresponds to the calculated value of the first beam width Bpx
calculated in step S754 (step S763). The laser radiation controller
31 then returns to the processes in the main procedure.
[0342] The details of step S770 are the same as the details of step
S170 described in the first embodiment and will therefore not be
described. In the present embodiment, the laser radiation
controller 31 is configured to set the XYZ stage 33 in such a way
that the speed of the fixed-speed linear motion is the scan speed
Vx calculated in step S755 and perform the scan radiation toward
the positive side of the axis-X direction.
[0343] 7.5 Effects
[0344] In the present embodiment, the laser doping and the
post-annealing can be performed by a single scan radiation action.
Further, in the present embodiment, the pulsed laser light supplied
from the laser apparatus 3 is divided by the reflectance variable
beam splitter 60, with one of the divided beams used as the beam
for laser doping and the other beam used as the beam for
post-annealing, whereby the pulse energy is used efficiently.
[0345] In the present embodiment, the reflected light reflected off
the reflectance variable beam splitter 60 is used as the beam for
laser doping, and the transmitted light having passed through the
reflectance variable beam splitter 60 is used as the beam for
post-annealing. Conversely, the transmitted light may be used as
the beam for laser doping, and the reflected light may be used as
the beam for post-annealing.
[0346] In the present embodiment, the scan radiation is performed
only toward the positive side of the axis-X direction. Instead,
first scan radiation toward the positive side of the axis-X
direction and second scan radiation toward the negative side of the
axis-X direction may be alternately performed on a row basis. In
this case, the first scan radiation and the second scan radiation
need to be so performed that the positional relationship between
the irradiated region Ad and the irradiated region Ap in the axis-X
direction is reversed. That is, it is necessary in the second scan
radiation that the second beam homogenizer 80 is used for the laser
doping and the first beam homogenizer 70 is used for the
post-annealing.
[0347] To this end, in the second scan radiation, the reflectance R
may be calculated based on Expression (29) described above under
the following conditions: .alpha.=Fd/Fp; and .beta.=Nd/Np. Further,
in this case, the first beam width Bdx of the beam for laser doping
satisfies Expression (33) below. The first beam width Bpx of the
beam for post-annealing satisfies Expression (34) below.
Bdx=REt/(FdBy) (33)
Bpx=(1-R)Et/(FpBy) (34)
[0348] In the present embodiment, the first beam homogenizer 70 for
laser doping includes the cylindrical lens group 71, and the second
beam homogenizer 80 for post-annealing includes the cylindrical
lens group 81. The first fly-eye lens 45a may be disposed in a
fixed position in place of the cylindrical lens group 71, and the
second fly-eye lens 45b may be disposed in a fixed position in
place of the cylindrical lens group 81.
[0349] Table 3 below shows a specific example of the parameters in
the laser doping and the post-annealing in the third embodiment in
the case where Et=100 mJ. Table 64 below shows a specific example
of the parameters in the laser doping and the post-annealing in the
third embodiment in the case where Et=40 mJ.
TABLE-US-00003 TABLE 3 Laser doping Post-Annealing Et 100 mJ Et 100
mJ f 6000 Hz f 6000 Hz Bdy 10 mm Bpy 10 mm Nd 10 pulses Np 100
pulses Fd 6 J/cm.sup.2 Fp 4 J/cm.sup.2 Bdx 0.02 mm Bpx 0.22 mm Vx
13 mm/s Vx 13 mm/s R 0.87 R 0.87
TABLE-US-00004 TABLE 4 Laser doping Post-Annealing Et 40 mJ Et 40
mJ f 4000 Hz f 4000 Hz Bdy 10 mm Bpy 10 mm Nd 10 pulses Np 100
pulses Fd 6 J/cm.sup.2 Fp 4 J/cm.sup.2 Bdx 0.01 mm Bpx 0.09 mm Vx
3.48 mm/s Vx 3.48 mm/s R 0.87 R 0.87
[0350] Tables 3 and 4 show that the laser doping and the
post-annealing can be performed in the present embodiment even when
the pulsed laser light has low pulse energy, such as 100 mJ or 40
mJ. The fluence Fd in the laser doping and the fluence Fp in the
post-annealing are settable by adjustment of the beam width Bdx in
the scan radiation direction and the reflectance R, as described
above. The values of the beam width Bdx and the reflectance R in
Tables 3 and 4 are adequately adjustable values. Further, the scan
speeds Vx in Tables 3 and 4 are adequately adjustable values.
8. Fourth Embodiment
[0351] 8.1 Configuration
[0352] FIG. 37 schematically shows the configuration of a laser
radiation system 2e according to a fourth embodiment of the present
disclosure. The laser radiation system 2e according to the fourth
embodiment includes a laser radiation apparatus 4e in place of the
laser radiation apparatus 4a provided in the laser radiation system
2a according to the first embodiment. In the following description,
substantially the same portions as the components of the laser
radiation system 2a according to the first embodiment have the same
reference characters and will not be described as appropriate.
[0353] The laser radiation system 2e includes the laser apparatus 3
and the laser radiation apparatus 4e. The laser apparatus 3 has the
same configuration as that of the laser apparatus 3 in the first
embodiment. The laser radiation apparatus 4e includes a beam
homogenizer 90 in an optical system 40e in place of the beam
homogenizer 43 in Comparative Example.
[0354] The beam homogenizer 90 includes a high-reflectance mirror
91, a partial reflection mirror 92, a cylindrical array 93, a
condenser lens 94, and a rotary stage 95, as shown in FIGS. 38A and
38B. The high-reflectance mirror 91, the partial reflection mirror
92, the cylindrical array 93, and the condenser lens 94 are
disposed in the optical path of the pulsed laser light in the
presented order from the side on the upstream of the optical
path.
[0355] The high-reflectance mirror 91 is formed of reflection
suppression films 91b and a high-reflectance film 91c formed on a
transparent parallel plate substrate 91a. The high-reflectance
mirror 91 is so disposed that the opposite surfaces of the parallel
plate substrate 91a are substantially parallel to the plane VH. The
reflection suppression films 91b are formed on the opposite
surfaces of the parallel plate substrate 91a in the region where
the pulsed laser light reflected off the high-reflectance mirror
41b is incident on the parallel plate substrate 91a. The
high-reflectance film 91c is formed in the region on which the
light reflected off the partial reflection mirror 92 is
incident.
[0356] The partial reflection mirror 92 is formed of a partial
reflection film 92b, a first reflection suppression film 92c, and a
second reflection suppression film 92d formed on a transparent
parallel plate substrate 92a. The partial reflection mirror 92 is
so disposed as not to be parallel to the high-reflectance mirror 91
but as to rotate around the axis H. The partial reflection film 92b
is formed on a surface of the parallel plate substrate 92a that is
the surface facing the high-reflectance mirror 91. The first
reflection suppression film 92c is formed on a surface of the
parallel plate substrate 92a that is the surface facing the
cylindrical array 93. The second reflection suppression film 92d is
formed in a region which faces the high-reflectance mirror 91 and
on which the pulsed laser light partially reflected repeatedly
three times off the partial reflection film 92b is incident. The
rotary stage 95 is configured to hold the partial reflection mirror
92 rotatably around the axis H. The rotary stage 95 is configured
to rotate the partial reflection mirror 92 based on a control
signal inputted from the laser radiation controller 31 to change an
angle .theta. between the partial reflection mirror 92 and the
high-reflectance mirror 91.
[0357] The cylindrical array 93 and the condenser lens 94 have the
same configurations as those of the third cylindrical lens array
48c and the condenser lens 46 according to the second embodiment,
respectively.
[0358] 8.2 Operation
[0359] The operation of the laser radiation system 2e will next be
described. The pulsed laser light that exits out of the laser
apparatus 3 and enters the laser radiation apparatus 4e is
reflected off the high-reflectance mirror 41a and incident on the
high-reflectance mirror 41b via the attenuator 42. The pulsed laser
light incident on the high-reflectance mirror 41b is reflected off
the high-reflectance mirror 41b and enters the beam homogenizer
90.
[0360] The pulsed laser light having entered the beam homogenizer
90 is incident on the regions where the reflection suppression
films 91b are formed on the high-reflectance mirror 91, passes
through the high-reflectance mirror 91, and is incident on the
partial reflection mirror 92. Part of the pulsed laser light passes
through the partial reflection mirror 92 and exits as first pulsed
laser light I1, and another part of the pulsed laser light is
reflected off the partial reflection mirror 92.
[0361] The reflected light is incident on the high-reflectance
mirror 91 and reflected off the high-reflectance film 91c. Part of
the reflected light passes through the partial reflection mirror 92
and exits as second pulsed laser light I2, and another part of the
reflected light is reflected off the partial reflection mirror 92.
The reflected light is incident on the high-reflectance mirror 91
and reflected off the high-reflectance film 91c. Part of the
reflected light passes through the partial reflection mirror 92 and
exits as third pulsed laser light I3, and another part of the
reflected light is reflected off the partial reflection mirror
92.
[0362] The reflected light is incident on the high-reflectance
mirror 91 and reflected off the high-reflectance film 91c. The
reflected light is incident on the region where the second
reflection suppression film 92d is formed on the partial reflection
mirror 92, passes through the partial reflection mirror 92, and
exits as fourth pulsed laser light I4.
[0363] The optical path axis of the first pulsed laser light I1 is
parallel to the axis I. The optical path axes of the second pulsed
laser light I2 to the fourth pulsed laser light I4 incline with
respect to the axis I toward the direction V by greater amounts in
the presented order. The first pulsed laser light I1 to the fourth
pulsed laser light I4 are collected by the condenser lens 94.
Specifically, the first pulsed laser light I1 to the fou